Bactrim and heartrate

Wierd. I have taken Bactrim before and had no incicent - that I can recall. Well, today I was diagnosed with Bladder infection - took 1st dose of bactrim and about twenty minutes later (as i'm walking into a restaurant), everything starts going haywire. First wicked itching, flushing of the skin - then eyes turn BLOOD red, face swells, tongue starts feeling fat and hurts - heart is pounding. I freak out - and throw some money on the table for a glass of tea - that I didn't drink - Husband rushes me back to clinic - as we both think I am having aniphilactic reaction. Terrified. Never experienced anything like it - my face swole up on the way - horrible. Wanted to scratch my skin off. Palms of hands, feet everything feels like its "asleep" and has needle like sensations. They ask if my airway is tightening (!) not yet? They give me a "steroid" shot (generic term I guess), and a Zyrtec. I start calming down on the way home - itching subsides and then chest pains begin - now I think i'm having a heart attack. I don't know if the trembling is from Bactrim or terror. I crawl into bed and start bawling - cuz I feel like I almost died. It scared the shit out of me. Husband paces and wrings hands. Now, hours later - I have sweats, fatigue (dramatic day), and heartrate is still elevated. Left tonsil hurts when I swallow. Yikes.