My partner doesn’t really have a sex drive?

So my partner and I (21F and 22M) have been together for about 6 months and honestly it’s going absolutely amazing. This is also the first relationship I’ve been in but my partner has never really been sexually driven. I’m always the one to suggest it and most nights he’s just not in the mood. Is this normal? I know most of the time he’s just really tired and stressed and it’s not because of me but sometimes I still worry. Also for awhile he was having a lot of trouble keeping an erection too, it has only been in the past two week that he had finally gotten off since the first time we had sex. I just don’t know what to do.