My 7-year-old is regressing and I don't know what to do!

I have no clue what to do anymore, so figure I have nothing to lose by turning to some internet strangers!I have a son and who is 7 and has recently started pooping himself in bed - on purpose. This has happened 4 times in just over a week.The first time, he was sick (at that point undiagnosed bronchitis and sinus infection), so SO and I brushed it off and chalked it up to a weird accident since he was sick. When it happened again 2 days later, we again assumed it was because he was sick and reminded him at bedtime to make sure he goes poop on the toilet before bed. Both times, I just cleaned him up and went on with the day.Well the third time occured before he was even asleep for the night. SO and I heard him go to the washroom several times, so my SO went to check on him the 4th time and could smell that he had soiled himself. This time we weren't so forgiving because he knowingly pooped himself. I cleaned him up and explained he lost his tablet and video games for the next day because this isn't acceptable behaviour for a 7-year-old. I asked him why he didn't get up to poop, and he told me that he was being lazy and didn't want to get up.This morning he did it again. My 7-year-old was just COVERED head to toe in his own poop. It was like I had an infant and they had a diaper blow-out. Once again, he was showered, bedding stripped, and he's been told he is grounded. Once again, he admitted it was because he just didn't feel like getting up.I just don't know what to do anymore! I work straight days, and this has made me late for work because I've had to shower him. He's also ruining his mattress because I haven't purchased a plastic cover for it yet. My apartment stinks, and it just puts me in a horrible mood to start my day this way.A little bit of background - my son was VERY difficult to potty train. He just didn't seem to care about being messy, and no amount of rewards ever seemed to help. He was peeing himself regularly during the day until about 8 months ago. He also still wears pull-ups to bed because he pees his pants every night (although this seems to be due to him being a very deep sleeper). He has not seen his biological father in close to a year and expresses his feelings if sadness and missing his dad.If anyone has some sort of suggestion, I'd love to hear it! via /r/Parenting http://ift.tt/2qIbydv