I'm new here, but I just read your post and wanted to share my experience. I struggled with the exact same things you are and I can really sympathize. I'm 40 years old now and I can tell you that you can absolutely overcome it and be totally confident in your sexual abilities.
You are actually lucky in that your length is normal... and there are things you can do to address the girth. Regardless, you first need to change your mentality towards sex.
I used to be deathly afraid of dropping my pants in front of a girl. Especially in high school and through my twenties. I avoided sex even though I had plenty of opportunities with beautiful girls... which made me beat myself up for not being "manly" enough. When I finally got up the courage to do it... I'd often struggle with getting an erection or maintaining it because I feared being judged for my perceived "shortcomings." This obviously made things worse.. it was a vicious cycle. Over time, I finally realized a few things that really helped.
The first realization I had was that sex is supposed to be enjoyable for both people... it's not just about you pleasing the girl. In fact, most girls will be turned off by someone who focuses ENTIRELY on them. Yes... you will want to add some moves to your sexual arsenal to give her a full experience... but don't become so focused on them that you forget to enjoy it yourself. Women love it when a guy is getting pleasure from them, just like us men get turned on when we're able to please a female. The bonus is... the more you get into it and enjoy it, the better you'll be AT it and the more she'll enjoy it!
Also consider what you actually want... do you want a bunch of one night stands or would you rather have 1 long term partner? I personally struggled with thinking my manhood depended on how many girls I slept with. Deep down I really knew I'd rather just take my time getting comfortable with 1 before jumping into bed. In other words... don't put pressure on yourself to do anything bc you think your manhood depends on it. There is nothing wrong with taking your time getting comfortable with someone before having sex! You can be upfront with girls about this too (and say it confidently, not bc you are shy... but because it's YOUR PREFERENCE.) It'll make you feel better being true to yourself. I don't know if you're like me in this regards, but just don't try to force yourself to be something you're not.
Also know that when you're older, most girls will have experienced many different dicks... and that includes many your size and smaller. Most girls are not size queens and don't expect a giant hammer every time a guy drops their pants. Seeing your average dick is not going to make them laugh or not want to sleep with you.
Try not to make the mistake I did and don't spend years focusing on the size of your dick. The gains in your dick will be very limited, but you CAN dramatically improve your confidence.
My advice would be to realize there are some things you can do to improve the size and appearance of your dick... and if you want to, do them. But seriously take your time and research fillers carefully because you can make things worse if you rush into it.
I would start with simple things like grooming. I personally think the right grooming can majorly improve the appearance of your dick, and believe me... appearance is VERY important, because sex is just as much mental as it is physical. I wouldn't completely shave down there... avoid the little boy look if you're worried about looking small. I've found that keeping my pubic hair trimmed short looks best (maybe a half inch or so.) I also pluck every hair off of my dick up to the pubic mound, including the underside (yes, with tweezers!) More dick skin exposed contrasted with a short trimmed pubes makes it look bigger and cleaner (more attractive to a girl.) You could shave your dick, but with tweezing there's no stubble and you don't need to do it as often. It stings a little, but you get used to it, and as a bonus... once you've done it for a while they don't grow back!
I'd also watch some educational videos on different sex techniques... oral, fingering for squirting (my favorite), and general sex positions, tempo, etc... but when you're actually fucking someone, don't spend too much time on these things at first. Girls will see it as compensating which will only draw attention to your insecurity. Foreplay is great for getting them worked up... but they want to get fucked and get you off too!
Once your'e in a relationship and having sex, you can start experimenting together. Your experience will grow and you'll be able to blow the minds of future partners with things you've learned. Toys are GREAT in a relationship too! Sometimes I like to use cock sleeves (silicone wraps that add instant girth), the good ol vibrator wand (blindfold ANY girl and make her cum in minutes), tying girls up, whips, etc... My girl and I go to the sex store and it's like a trip to Disney for us, lol. Have fun with it.
There's no reason you can't have an amazing sex life, so don't put so much pressure on yourself. Learn what you really want and what you're comfortable with and OWN IT.