Arm hurts after work or lifting weights.?

My left arm was sore for several weeks awhile back and I figured it was from my job. I work at a dry cleaner and when the cleaned clothes come in I have to put them all in numerical order and hang them up on a rack above my head. I figured it was the repetition so after babying my arm for a few weeks the pain went away. I switched shifts so I am no longer there in the afternoons when the clean clothes come in and have had no problems with my arm in several months. I just joined a gym and lifted weights with my teenage son yesterday and this morning the same pain was back again. I couldn't even use my arm to put on my name tag at work because my left arm won't bend to my chest. I can't hold anything even slightly heavy because my arm won't support it and any sudden movements send shooting pain up my whole arm. I wrapped it in an ace bandage today to prevent me from moving it too much but the restrictions are pissing me off because I'm not use to my body not doing what it's told. My current plan is to continue lifting weights just smaller ones and build back up. I use to lift weights all the time when I was younger and have taken several kinesiology and nursing cles so I know how to lift properly. I just want to know why my arm is giving me grief, how to fix it and prevent it from happening again. I don't have insurance so I am not going to go to a doctor, they will most likely want to cut me open anyways and there is no way I'm allowing that. My mother in law had nerve surgery in her arm and now her pain is worse than ever so forget that, it's not an option. Any physical therapist/ personal trainers out there who have a better plan or recommendation? If it helps any I am an overweight 39 year old female who is just starting to get back into shape because I get out of breath and chest pains walking across campus at college. I use to work out a lot in my younger days but then kids, disabled husband, work, returning to college.... life got in the way and I got too busy and couldn't find time anymore. The chest pain and shortness of breath just walking from my motorcycle to cl was a real eye opener. I refuse to die young of obesity related heart problems damn it. I plan to teach my great grand kids how to ride a motorcycle and celebrate my 100th birthday at Sturgis.