Sudden floating axolotl?

Hello everyone, I got a new white albino axolotl about a week ago, he is about six inches long and has been very healthy while I've had him. Usually he spends his time laying on the bottom of the tank, he might walk around a little bit but has been very lazy and docile.

I last fed him blood worms two days ago, and was about to go prepare some more food for him today when I noticed that he was having problems staying at the bottom of the tank. He has been perfectly fine all day until now, his rear end is pulling him to the top of the tank and he is very unhappy about it.

He is not bloated at all, and I have no idea what prompted this. I could greatly use some tips on what to do, I hate to see him so stressed out! If he's still struggling in about five minutes I plan to remove him from the tank and put him into a shallow container so that he can still lay down. Not sure if I should still feed him? Please help!

He needs to poop, thats all.
At 6" he should be on earthworms, not bloodworms, that may account for the floaty bum.

I am planning on getting earth worms soon but as of the moment I only have blood worms, poor thing wasn't even eating at the pet store I got him from. I'll wait and see if he produces any waist and calms down again. Thank you!