What Can Cause Blood In The Vagina After Having Sex?

I had my periods on 9 september..this month i had 4 days early periods. That ends on 15 september..it take a week just like my usually periods stay a week. After that i had sex with my husband on 16september. Everything is normal. Then i have again sex with my husband on 19 september.so after the sec when i go for a shower so just put my finger inside the vagina to clean out all the semen before my shower.but i saw blood in my finger.its red and fresh blood. After that next morning i again put my finger inside but now the blood is little bit thiick and in lite red brown color.i dont know wat is this.. Is this a miscarriage or wat ?? I also have pain in my stomach from 2 1/2 years..sometime the pain is on and sometimes its not.sometime i had pain on the lower abdomilnal and sometimes its on the belly bottun..i go to a dr she told me to do a sonography..i did the sonography then she told me that everything is fine i just had a little swelling in my stomach she give me some medecine..but its not work And now again i am having the pain in my stomach and blood in my vagina..what is this ?? A miscarrigae ?? Or something major problem inside my body ?? And one more thing the blood is not getting drop..its just inside.iTs not coming out