Help!

So I am pretty inexperienced and the guy I'm with is not. He tells me positions to go into and I happily oblige. Lol but I recently lost over 100 lbs from bariatric surgery and have a little bit of a difficult time being on top. Idk if it's nerves from still feeling bigger or what but it doesn't work out very well and I feel like it's my fault and that it's disappointing him. I'd like to take control when on top but he does a lot of the work without really giving me a chance and then he's going and I'm trying and it just gets out of sync.

Any tips?

Also I am inexperienced and he knows that, I want to surprise him somehow, but don't know how. Any suggestions for things that drive your guys crazy in bed?