Hey guys!

So I got my first ball python three weeks ago, I have a rosy boa and have had her for 3 years now, no problems. Before I got him I cleaned everything in the cage including the cage with a 3% bleach solution. I got the snake from a pet shop (my first wrong decision in this situation) and he was "about a year old" (unsure store employee quoted). Anyway, before I got my baby I made sure to do a ton of research on BPs and the care and I really should've realized this when I got him, but he was in the middle of a terrible shed. He was shedding in pieces and his eyecaps were retained. When I got him home I put him in my 10 gallon tank and let him get used to it before handling him. When he got comfortable with me I soaked him and got everything but the eyecaps off since he was head shy. He ate regularly for the next two weeks, furry mice that were thawed and he had no problems. He was incredibly sweet and social with my friends and whoever. Wanted to check him out. He would love to roam around my room and explore places in my bed. I got the eyecaps off by using the tape method, which obviously was a huge relief. About 3 days after his third feeding, I noticed that his tail had become terribly bloated and his anus was puffy. I soaked him for 5 minutes thinking it was constipation, dried him off and put him back in the cage. The bloating wasn't the only problem though, he lost motor function in his tail. He would no longer wrap up into a ball and no longer use his tail to hang onto my hands and branches in his cage. He would flop around and fall without realizing why he fell. I checked his mouth to see if he had any respiratory problems and it was a grayish color. He would breathe heavily randomly. This all happened the day he died, giving me no time to take him to a vet and no time to figure things out. When I came home from running errands he was in the same position he was in when I had left him. I knew something wasn't right. I opened the cage and poked him, rubbed his scales, nothing. I picked his limp body up and tried for signs of life but there was nothing. My sweet little man was gone. I was too heartbroken to take him to a vet to figure things out so I've buried the body and left the tank, which eventually I will clean and everything.
I want to believe that what killed him was IBD, but when I got him he seemed fine, and after cleaning his cage completely I can't find any mites. Also, does IBD kill snakes that quickly? I mean it happened over a span of only 2-3 days. He was eating perfectly and acting perfectly before he got bloated and breathed heavily.
His tank was ten gallon, I just ordered a twenty gallon for him because he had been getting to two feet and i wanted him to have a big environment. He had, on the warm side, a log to lie under and to bask on top of, a light that i would change at night to an infrared bulb and aspen shavings. On the cool side I had a skull hide, a medium sized water bowl that he bathed in before he got bloated (maybe that hints something?), a pile of moss and two leaf plants for him to climb on. The cool side was always at the 50% humidity mark but when he had his shedding problem I would mist the cage up to 70% occasionaly, the warm side was always mid to low 80 degrees fahrenheit.
I just feel terrible.
Please help me understand?