Sore back

Ashley • I'm 23. my son is 2 yrs old. And my bf is 24 We've been together for 8yrs in sept. Expecting our baby girl April 14 !!
Any one else having a really sore / tight lower back? Mine started last night and a warm bath didn't ease it up. If i lay on my left side it hurts but my right side so much better. I'm wondering if it's a kidney infection or another uti? Sigh I'm over thinking