retroactive jealousy

me (f21) and my girlfriend (f20) had been dating for 4 months and before i came into her life she had a long term relationship (they broke up late last year).

this is my first serious relationship and in my 20 years of living ive never had sex or kissed anyone. she was my first in everything and i know i wasn’t hers and it was her ex. i get so insecure because im still new to things and she probably had done everything with her. :(

recently her ex pops up randomly on my social media, like on my tiktok and instagram. whenever i see her i get this gut wrenching feeling and i feel like my heads gonna explode. i love my gf and i know she loves me too but i just can’t stop thinking about it sometimes and feel insecure.