When drugs cause allergic reactions, these can go on for days after stopping them. The Bactrim is a long acting one besides.

So if after 2 weeks you still have this, I'd see the doctor again.
In the meantime, try some Benadryl 50mg 3 times a day, and Zantac 150mg 3 times a day and see if this resolves. Both are histamine blockers and often used together for drug and food reactions.

I think you need a B12 test, and Vit D test. Your B12 should be 400 or above. Don't accept "normal"...get the numbers. Many doctors think 200 range is normal and it is NOT. Anemia may be due to low B12, as well. The target for the D test is 50-80ng/ml. Don't accept 30 as normal either! It is sad but true that many doctors don't have accurate ranges for these tests in US. So patients have to take over in this case for themselves. You can ask the doctor if in your blood work, the MCV was elevated. If so, this points to low B12 also.