Finishing second, which has become terrible

When my husband and I got together, we would have sex for several hours and many times that would last. Now that we have been together for 4 years in total, something new has started in the last year or so, he finishes within 5 minutes. We have talked about it and he refuses to see a doctor about it. I’m so frustrated because we never get to enjoy sex any more. I literally have to finish myself off or he has to play with me but it’s never the same and doesn’t feel as good. I want “ him”. I just had a baby 5 months ago and we the night to our selves for the first time since she had been born and it seriously lasted two minutes. We have had sex since we have had her but what the hell is causing this because I’m to the point that I’m done having sex. I have tried talking to him about it and he shuts down or he turns it to me like in have a hard time cumming. I don’t, but I need it to last longer than 5 minutes and I want more than fore play. Need advice because I’m to the point where I want to spike her food or drink with viagra🤦🏼‍♀️