Tremors after eating

I keep experiencing tremors after eating and afterwards my back gets incredibly stiff and I start spasming everywhere. Also have pain and nausea that comes and goes in my lower right stomach, no pain when I push on it. I went to dr 3 weeks back and was prescribed antibiotics for a UTI I took for 10 days. They also said my potassium was low but it’s since returned to a normal state. I was experiencing these tremors prior to taking antibiotics but not quite as bad. I have a history of back issues and scoliosis but it’s never gotten quite this bad. My neck has been stiff up the sides for about 3 weeks with no relief even when nothing else is bothering me. The rest of back pain will ease up after 3-4 days then I’ll feel semi-normal and healthier for 2 days and not experience tremors then it will hit me harder than before and throw my back out. I’ve been doing stretches for shoulders and lower back, helps at times but other times I hurt so bad it feels helpless. My throat has also been irritated but could a separate issue. Does anyone have any idea what I might be dealing with, or if it’s something unserious that’s maybe just been heightened by the antibiotics (doxycycline) I was taking? The doctor today sort of dismissed it as that, but I’m still concerned and don’t feel they did much to check me out today.