sex tips??

So i've been messing around with this guy for awhile and we've been good about "mixing it up" in the bedroom but i still have a really difficult time getting off. Part of it could be from me being so uncomfortable about my body/weight, but i feel like i've been able to loosen up about that and it still hasnt helped much. I know plenty of women aren't able to just from penetration, so does anyone else who has this problem have any tips for positions or other sex play that will help with clitoral stimulation? Or if he's going down on me how do i direct him where to go without being bossy or awkward about it?