What Causes Abdominal Pain And Tender Breasts?

Hi there please can you help, ive been experiencing nausea, tiredness, very tender nipples which are slightly darker then normal, i have always had blue veins in my breasts but they are slightly more noticable, i always need a wee!, i was due my period between 2-4 days ago, two days ago i had a clear jelly about an inch long sitting in my pants, that was in the morning, lunch time it again was there but had a very slight tint of pink, in the afternoon it happened again but with a slight brown tint, i have been having abdominal pains for 4 days now they come and go but when i have then either left or right side they are sharp and lasts awhile, my lower back really aches, i have done 2 pregnancy test both neg, i have two children and didnt find out till 9 weeks and 15 weeks with them. Its the abdominal pain that is worrying me any advice please?