Non stop lower back pain and pelvis

I had it bad last night, but I was able to sleep a few hours today it’s been bad, non stop but I felt like I had to clean my apartment all over so I did, bf helped me because I decided to move things around (he moved them for me) which made a mess but it is now organize. And I feel like I accomplished something. But the pain is horrible it’s not coming and going it’s been non stop now that I’m relaxing. L&D told me to wait for 4 hours if it doesn’t go away after trying Tylenol. But since I’m not having contractions I should be okay. My belly is so tight... I’m 35 weeks but baby is measuring 3 weeks ahead. Has this happened to anyone