Hello and welcome to MedHelp's forums. Thanks for your question and how exciting to be having twins! I'm sorry to hear you are so uncomfortable. Swelling of limbs is very common during pregnancy especially after the 20th week. However, if you have any other symptoms associated with it such as headache or vision changes, you do need to call your doctor. I assume they are monitoring your blood pressure and protein in urine?
You are nearing the end of your pregnancy and while we hope that you go full term, twin pregnancies are considered full term at 37 weeks with the average time being 36.5 weeks for most. You are almost there! The idea if all issues such as pre eclampsia, high blood pressure or blood clots are ruled out is to make you as comfortable as possible. Drinks lots of water which helps swelling (flushes it out) and prop your legs up. When they are elevated, it will help with the swelling. Limit salt. If you can get a massage, this can help as can going for a swim. These are known ways to decrease edema during pregnancy. And don't sit with your legs crossed.
Here is some information regarding discomforts of pregnancy and you'll see in the third trimester, this type of swelling is the first thing listed. https://www.webmd.com/baby/understanding-pregnancy-discomforts-symptoms and here is a good read as well https://www.medhelp.org/pregnancy-health/articles/Swelling-During-Pregnancy-Your-Symptoms-Manual/2001.
Let us know how you are doing and at this point, you are probably seeing your doctor weekly until delivery. Continue to monitor this and let them know of any and all changes. We wish you the best.