My bf and I had intercourse and now my vagina is very swollen and itchy. What could this be from? I've been tested for STDs and I was clear.

Probably yeast. A yeast infection will commonly present with itching, especially after intercourse. Other things, such as an allergic reaction to creams, condoms, spermicides, bath salts, perfumes, etc can also cause itching. Your doctor can easily evaluate you to see what is going on.
Latex allergy. If you used a latex condom, is possible you are allergic to it. Keep in mind latex condom are the only one that may protect you from std. Sheep skin condom may prevent pregnancy, but not std.
Physicality. While allergy, and / or infection are possible, sometimes there is swelling after intercourse if prolonged, seomwhat rough, or if vaginal dryness present at the time.

Related Questions

My vagina is swollen and itchy, this is the thrid time in five years and no one knows why. I have been cleared from any stds. I need help.?

Vaginal Health. First of all, eliminate all perfumed or deoderant soaps from the vulva and use dove, caress, or ivory which are mild and non-irritating. Eliminate thongs, and use cotton crotched underwear. Get out of wet bathing suits, and exercise togs immediately after use. Finally have a gyn md do a wet prep (or smear) of the vaginal fluids for microscopic immediate assessment of the content for infection.
Be seen. It is possible that it is an infection that is not an std. A subclinical yeast infection, for example, or perhaps something else. It could also be an allergic reaction to something.