Sex deprivation: How long is it permissible for a husband to not have sex with his wife?

Salam Alaikum. Pls I have been married for 6 years and my husband doesn’t really have sex with or even just intimacy with me. I want to know pls how long is permissible for a husband to leave his wife without touching her with no excuse while they are staying together. He could go 3-4 months without sex and even when I make moves, he complains to be tired from work. Thank you.