Hi,
Lack of interest in sex can be due to many reasons like history of abuse/rape,
vaginismus, fear of sexual performance, fear of
pregnancy, fear of getting
STD, self consciousness/shame for ones own bod, etc. Sex is a beautiful thing you need not get conscious of your body or performance. Just try to relax & enjoy.
Presently it looks like vaginismus from which you are suffering, visit a gynae & get your pelvis physically examined. The gynae will look for any infection, scar or growth that may cause the pelvic muscle contractions resulting in preventing sexual intercourse.
Get treated, if you have no pathology causing it then start doing regular pelvic exercises & get yourself emotionally & physically ready for a man. Take your sweet time, don't haste. You are very young, stay away from addictions, go for protected sex.
Make sure you are with a man who loves you, with whom you are comfortable & close before indulging into sex right away.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr Nupur K