Light back pains on the left side

It's more like a throbbing or light shock feeling. Been having little pains here and there all day. Last night I had a quick punch feeling on my upper left side last night which was probably gas. Went to get a pedicure and I couldn't get comfortable, my bra felt too tight, the massage chair wasn't comfy, and I didn't want to be in my baggy jeans anymore. Took a pregnancy test a month and couple weeks ago and came back negative with evap line. I have some pressure in my uterus and back