Is working three days a week neglecting my baby? Is needing 45 minutes at home to work out too selfish?

I have a three month old, and since he was born, I have not left his side except long enough to go to a haunted house in October, and an hour and a half last weekend to go to dinner with my husband. He is really fussy, and wants to be held almost continuously. I don't complain about that, cause I know soon enough he will be all over the place and not want to be held, so I cherish this time. What is frustrating though, is that I gained a lot while I was pregnant. I didn't worry cause I knew when I started running after I delivered I would drop it all. I thought I would be able to have my baby in front of the treadmill (in the fitness center of my apartment complex) while I ran. Not the case. He screams like he's been abandoned when I leave him in the bouncer (in front of me) for more than 5 minutes, and sometimes not even that long. So I hold him. I have even gained an additional 10 lbs cause all I do is sit on my but all day and hold him. All I ask of my husband is to watch him for 45 minutes so I can go run and take a shower afterward. He won't do it. Says the baby is my responsibility, and I knew what I was getting into. He says I need to get my priorities straight and not be so selfish. I returned to work this week, planning on working three 10 hour shifts. After the first day, I found out how hard it was for my baby to be without me that long, the next day, I rearranged my schedule so I was only working three 8 hour shifts. My husband said I could only work 2 days a week, period. Those two days his grandma would babysit the baby, and he wouldn't have to. I look in the mirror and cry sometimes because I am really overweight, and I feel frustrated because I have the drive to run, I just can't get there cause my husband won't watch the baby. He says I am selfish, and tonight he said he can't believe he married a woman that is such a selfish mother. I love my baby so much. I kiss on him and play with him and sing him songs all day. I am always reading to make sure I do things right. But is it selfish to want to get out of the house to work a couple days a week just for my sanity? To talk to adults, let alone that fact that two days a week won't cover my bills. I can't afford it. Is wanting 45 minutes away from my baby just so I can get healthy, shower, and even eat while I am not nursing really selfish? My husband gets to work out everyday, go run errands, go to the sports shop, etc. Am I being unreasonable to expect him to be more of a father than that? OR AM I CRAZY?