Was swimming after lipo a bad idea?

Thank you for your question.  It sounds like you have been quite compliant with your prescribed post operative care---and it's unlikely that swimming 3 weeks following liposuction will lead to an adverse cosmetic outcome.  As you've surmised, you will indeed have persistent swelling at 3 weeks post liposuction.  I typically explain to patients that it may take up to 3 months for acute swelling to resolve, and that changes in the contours of your thighs and flanks can continue to occur for up to 12 months following liposuction.  I realize how difficult it is, but you must have patience when it comes to plastic surgery!  Best of luck to you.

First of all, congratulations on your liposuction, nyclife!
In general, you can already swim three weeks after liposuction as long as you’re completely healed. So I don’t think swimming contributed to the lack of results you see.
Three weeks is still too early to see the final results of lipo since there’s still swelling at this time. Swelling will subside around six months to one year, so don’t worry about it for now.
Just make sure that you go for follow-up checkups with your experienced and reputable plastic surgeon.
Best of luck!