Most men find it so exciting to be with their woman that they're not at all interested in wether or not her breasts hang down at the wrong angle or she has a fold of extra fat around her waist. What's exciting for a man is that he is looking at her, feeling her, and being mutually aroused. If he loves you on top and you think it feels good, believe him when he says it's erotic and exciting to him. Afterall, he is probably giving you physical proof that this is turning him on.
Many men love full-figured women.
Believe this and enjoy it. Don't be your own worst enemy by feeling insecure about something you don't have to be insecure about. You can however make a penis feel harder, more full of blood, which might make it feel longer. Viagra for example drives blood more efficiently into the penis and makes it more fully engorged and harder. This will make the penis feel very hard and men say it makes for a more extreme orgasm.