I can’t get past this block with my girlfriend

I (18M) have been in a long distance relationship with my girlfriend (20F) for 2 years. A frequent problem is that i feel like im “blocked” sexually, sometimes it’s because i feel like there’s not enough affection but it’s not that all the time: how should i fix this? i have no idea on how to act. i already talked about it with my gf and she does what she can about it, and sometimes i also feel a kind of pressure about having sex. let me explain better: as of now we’re in one of those periods in which i feel “blocked”, and yesterday i told her that i didn’t really feel like having sex that night in a worried tone, like i was afraid to tell her, and she replied “don’t worry, i don’t want to have sex either” and i felt kinda relieved, i didn’t feel that pressure anymore.