No wonder you are in pain. Men's chamois are shaped quite differently than women's, for obvious reasons. While I guess some women can wear men's stuff, I would think that it might be a real issue for most.
There are nice women's shorts in XL, XXL, or plus sized, right here on TE. Ask them for help. Terry makes a lot of their shorts in plus sizes.
I know you said money was tight, but I hate to see someone's enjoyment ruined by a pair of shorts. I have experienced that feeling of having to "go," but it was really irritation. For me, it was a saddle issue, as well as saddle position.