Need Help ASAP

I've been feeling this pain on my lower back, (nothing sharp, just pain) right below my waist. before it use to hurt on my left side, stopped hurting when I was on my period, then a week later it's on my right. it hurts when I bend, or just even standing sometimes. it comes and goes, but when it comes it hurts like a...! first I thought it was urine infection, but it didn't hurt or bled when I used the restroom, didn't feel nauseous, or all the other symptoms. it just hurts on that certain spot. also, I've been having cramps and it's only been a week and a half after. I get my period this month around the 25th and I don't understand why I'm having strong cramps as if I was beginning to get my period, also feeling bloated. has this happened to anybody?