Sulfamethoxazole and stiff

I have been taking Sulfameth/Trimeth for a bladder infection, one pill 2x a day. I started taking it on Thursday and felt pretty good for Thursday and Friday. Saturday I started having major headaches, feeling itchy all over, feeling a little bummed out, and felt a bit short of breath. I woke up today (Sunday) and had HORRIBLE pains in my left arm and my heart felt like it was beating much faster than normal. I took my pill and had something to eat, and took some Tylenol for the headache and I started to feel a bit better.

Once the Tylenol started to wear off, the pain in my arm was back, along with my left leg. It sort of felt like I had exercised way too much and that it was just stiff and sore. I've lost my appetite and am extremely tired but feel unable to sleep. Also today I feel depressed and angry and the littlest thing will set me off. I have 2 days left of this pill, I can't wait to be off it, and I will never take it again. I am contacting my doctor tomorrow morning to see if I should continue taking this as long as it was prescribed, or if I should just stop right now.

Why do doctors prescribe this when there are things that work much better with less side effects!?

I started taking Sulfameth for a urinary tract infection and got the worst gastro-intestinal bloating and gas ever! Then, my neck started to get stiff and I got a headache. This after only three pills. This stuff is bad news!

I was given this drug from ER doctor for a restiant strain of MRSA, 10 days of pills. I stopped taking the pills two days short. I had night wsweats, constant tired,. then two weeks AFTER stopping this medicine, Every Joint and tended in my body swelled up for two weeks, leggs were burning and stiff. hips hurt... Went to er told nothig they could do. Wend to my doctor who perscribed oral sterioids, they started working 5 hours after taking first two pills. I AM TWO DAYS OUT OF A 10 DAY REGIMENT ON STERIODS AND STILLHAVE JOINT PROBLEMS.. I WILL NEVER TAKE THIS MEDICINE AGAIN!

Taken for UTI. 26 years old, Asian, 5'2'', 120 pounds.
After 7 days of taking a 10 day RX. on the 8th morning I forgot to take it but got an undecent trade off with an body rash as follows:

1st day: rash with no itch on the torso. progressive during the day to my knees and neck with minor itch. sleepless night
2nd day: head to toes rash (red spots not clumped but individual in various sizes within half an inch). ankles and knees stiff. warm face with no fever.