I Did Some Furniture Building And A Lot Of Bending

I did some furniture building and a lot of bending lifting and cleaning yesterday and have deep penetrating sex with my husband the night before. Early this morning around 330am I noticed some blood in the toilet and when I wiped. However haven't noticed anything since and have had no other symptoms. I'm 7 weeks pregnant with my 2nd pregnancy. I have a 2 yr old born c section and did not experience this with her. Why am I bleeding??