HELP! He can’t stay turned on or get turned on

Hi ladies! I need some help!

So when I first met my partner we use to have such great sex and so often, we couldn’t get our hand off each other. However, we haven’t had proper sex in 2-3 months because he can’t seem to get turned on nor stay horny because he would loose it. Do you girls know why? Does your partner do this?

I don’t think he’s cheating, but he use to take drugs and stuff but has stopped a year ago. However, he would go through these phases where he would loose it but it would only last a week or two - never this long