Sex life going down

Taylor
My husband and i have been together for 4 and a half years now and I still have a very high sex drive, but my husband seems to not want to have sex anymore... he used to beg me to have sex with him and now it's always me begging him and him saying no, he's not in the mood... I had our son 7 month ago and since I had him his sex drive has plummeted... my vagina is just as tight if not tighter now seeing as we have more trouble getting it in than we did before I got pregnant so I know that's not it and I'm still the same size everywhere that i was before i got pregnant... I'm not sure what to do. I've tried dressing up for him, I've tried spontaneously starting something and everything else I can think of, but 99% of the time he says he's not in the mood... I highly doubt he's cheating, but to go from wanting sex all the time to almost never wanting it is scaring me... what should I do??