concerened,... What is wrong with me? I am 25 (will be 26 soon) and my husband and i are trying to have a baby.

This is the situation, i did get pregnant about a year ago, but because of the situation we were in, we were not ready (financially) to have a child. I dont believe in bring a baby into the world until i am 100% ready to take care of them financially. I had an abortion. I got on birth control after that. In January we decided that we were ready to try again so i got off the birth control,.. we are almost in May and so far no cigar.

This is the problem,.. i was suppose to get my period last Friday and its Monday and i still have not gotten it. I have taken 4 pregnancy test and all of them have come out negative. I am experiencing major back pains and abdominal pains,.. could i of had a miscarriage? i have not had any bleeding at all? and i if am pregnant could it be that i am taking the test to soon? or could i just be stressing so much that its causing me to be late? if so, when would i want to see a doctor

Summarized question: How soon can you take a pregnancy test after your missed period? Can you have a miscarriage without any bleeding?