Exercises for Back/Hammy Pain

I’ve been struggling with an injury for over a year now that I can’t put my finger on. I often get spasms/stiffness in my low back, hamstrings, and a tightness in the very top and middle of my calf. When sitting, the pain is localized exclusively in the belly of the center of my hamstrings and calves. The pain is not sharp and I think is just a result of the tightness or more severe spasms. I also have a tightnes just above my waist on the sides and outer edges of the back. I also get a lot of tightness in the back when doing sit-ups (not pain) A stretching regime helped remove problems in day-to-day activities but this pronblem still arises when lifting.

Could anyone give me an idea of a diagnosis and some suggestions for exercises to fix this?

A year?! Go see a doctor.

Stop lifting with your legs until you see one, and get HIS/HER diagnosis. We wont be able to tell you shit online.