i just cant get this thoughts from my head

If people could do that, it would be the end of our species. Like pandas who don't want to mate. Pain is a signal that something is "wrong". You have put so much of your life into your hobbies, interests, and career training that you have left yourself lopsided and in need of training in this other area. Conversely, some people pour themselves into "relationships" and thereby leaving those other areas undeveloped in themselves - career aspirations, developing their own interests/hobbies separately from their spouse, etc. You are not alone, nor unique in your path - even those that you envy might be looking over at you and envying YOUR freedom and ability to enjoy things on your own, which they (having responsibilities such as kids) cannot. "The grass is always greener on the other side..."

One thought: between the age of 15 and 25 is 10 years. It is too late to recover that lost time - all the interactions you would have had (discussions/conversations, dates, kissing, holding hands, etc.) Between now and age 35 is also 10 years, except you are smarter and can be more intentional about learning things than a 15-year-old. You CAN make up that lost time, probably in well less than half that time. By 30 you can have totally caught up, if not to other 35 year olds then at least to other people like you who are still 25, with your 5 years of intentional training in learning how to have relationships. Why are you giving up? Well, you do you and if you want to give up, especially just for now to take a break, then by all means do so - but I wanted you to realize that it IS possible, it is NOT hopeless!

There is a saying along the lines that to truly judge another person, you need to have walked a mile in their shoes first. You sound like you are disconnected from society in some ways - perhaps you have parents but do not feel comfortable talking with them, at least about such matters - so find others who can mentor you. Maybe join a "church" (the USA method of handling such matters, regardless of "religion", so find whatever equivalent is in your area, sorry but I would not know what that is even if I knew the country you were in, not having lived there myself), or something along those lines. I see elsewhere here on this thread that you seem to lack confidence in your abilities, like not wanting to show off your artwork. But if you do not step out then you will never grow. Find a way that works for you to engage with the world - it just HAS to be done, and you WANT to, right? So find a way, ANY way. You have already started by posting here:-). But online will never be enough - you need closer, more personal interactions, and to be clear I do not mean (just) women but rather older men who can help you, and quite frankly older women as well, who can help you in many numerous ways to learn to talk to younger & sillier members of the same gender. And maybe therapy if you can afford it, or just self-guided as you are able.

Pro-Tip: do not let your feelings master you. Feelings of jealousy are not "wrong" - they tell you what you currently lack - but they will often lie to you, like if you could just get this "one thing" then somehow you would be happy. But it will not. If you need proof, pay a prostitute to kiss you or even go for all-out sex - it will feel good(-ish) but will not satisfy that particular itch that you have. You need deeper than that, but even if you had a full-fledged relationship you STILL need more than even that. It is easier for us to see that from the outside than for you, who are younger and therefore lacking experience, to see it from the inside and in the midst of your emotional storms. You need to be connected to SOCIETY - friends, mentors, romantic partners, places & people for you to serve at & alongside with. Ideally you would have so many irl interactions that you would barely find the time to visit us here on Lemmy. But baby steps. Maybe start by doing your hobby without letting this bother you too much for ONE WEEK. And then... maybe another week as well, but eventually, see where that road takes you.

Also note that you are very judgemental. You judge yourself quite harshly, and not entirely based on facts - calling yourself "ugly" and not merely thin but the pejorative "skinny". With this attitude, you WILL destroy whatever relationship you manage to get yourself into - you will find some fault with her, and tell her about it, and she will feel deeply hurt and need to pull away from you. Your battle is not to find this acceptance and love from another person, but... if you are okay to hear this at this time, to find acceptance and love from YOURSELF. You have to give it to get it. Practice on yourself first?