I've lower abdomen pain, very low and my lower back, and hip pain on my right side for about a week. I went to doctor and he thought it was back strain, but this evening it has been more painful. I also, am constipated and taking Colace for this. I don' t have a fever and not nauseated. What can this be?

Constipation can cause these symptoms.

I have this too! Realizing how many possibilities are involved, especially in my 60s.
Mine coincided with intense pain down the front of my leg on 2/27. That pain has lessened, but the constipation and feeling of intestinal fullness and discomfort remains, and I can't stay on my feet for very long without general leg pain.
I did have ultrasound for a blood clot of the large leg vessels.
Narrowing this down depends on age, gender, general health, and so on. Anything from appendix to ovarian cysts to pinched sacral nerves to IBS to rectocele and on and on.
I'm waiting to see how it goes because I'm hoping I just strained something when lifting some boxes, and maybe my bowel is just in some sort of shock temporarily. I can't take a laxative because that just brings out a little bit at a time too, only looser, and brings back the intense pain down my leg.
Join the club!