I've been taking medication for hypothyroid since 1987 with some ...

I've been taking medication for hypothyroid since 1987 with some changes of dosages and brands based on lab tests and, I suppose, doctor preferences. Until 2 days ago I was taking 112mcg Levoxyl, with no side effects, I thought. Recently, my pharmacy ran out of the usual brand and substituted another brand with 7 pills until their shipment came in. No problem. Without medication my throat and tongue starts to swell within 3 days and in 10 days I'm sitting around trying to see how little I can breath. Even that wasn't so bad but the heart beat slowing and then quickening gives an unsettling adrenaline type feeling. OK back to the switch. I retrieve my usual brand when it came in and was 5 days into that when BAM!. intense chest pain woke me up 2:30 in the morning. I took aspirin and TUMS, thinking I covered everything. The pain radiated from the center of my chest to my back, continued tingle sensation down the undersides of my arms, and achy ears. It even hurt to breathe. 30 Minutes later, and after unsuccessfully trying to minimize symptoms using WebMD, I decided to go to the ER. Lots of test later that rule out heart they said I was taking way too much Levoxyl and wrote a prescript for .75mcg. Since researching I've notice other symptoms I attributed to age (am 52) painful joints especially hands, wrist, feet, ankles, and knees that I've been popping Tylenol for 2 years. Stiffness. I'd like to blame the 20 pound weight gain in 8 months on it too but seems like I should have lost weight. Since I can't go without medication it seems like I'm but to the hunt and peck method of finding the right dosage and brand. Any recommendations on which direction to take?