Help Please!!!

So my boyfriend and I have been together for 4years on and off. We have two kids together and we are trying to make things work. I'm trying anything and everything:) well he has gotten me to do a couple threesomes and I know he wants to do more but he Also just wants to sleep with other people because I don't like "trying new positions" ( I'm very insecure with my body after having kids) I told him I was fine with it but I want to learn more thiNgs in the bedroom ( I'm up to try anything that will blow his mind away! Haha)and try to get over my insecurities with my body! Any suggestions or tips that would help me out in any way?! And he is a very experienced person in the bedroom and I'm not! So help please!! Lol