What Causes Swelling In The Legs & Abdomen With Heavy Periods?

Have had problems with painful swelling of legs, ankles, feet and swollen abdomen. Started with a missed period, thought I was pregnant. But im not. The swelling and pain keep getting worse. Has been going on probably 6 month now. I m on my feet a lot. But even after a month off work it didn t change. Also dehydrated. Ive tried lowering caffeine intake, drinking more water, changing my diet. But still keeps getting worse. Any insight into what it could be and y it started with a missed period? Im 36 and have an 18 year old son. Never missed periods before. They haven t been irregular since the missed one, but they have been heavier. Not sure if there s an association between the missed period and the painful swelling