Can Fluttering Sensation In Stomach And Lower Back Pain Be Signs Of Pregnancy?

My husband and I are trying to have a baby, this will be number 2 if it ever happens, we are in the process of going to a fert. doctor, to help, see what is wrong, because about 2 years ago I had a miscarriage, the doctor that delivered my first one, is a dinocologist, sorry for mispelling, anyways, he has done all he can do on advice, etc... So I had my menstrual cycle around Ja.19, the nurse told me to have sexual intercourse around 30,31 of January, might be a chance of us getting pregnant. We did that, this week I am feeling different like my stomach feels like something is fluttering inside, I feel tired more than usual, today had lower back pain, also using restroom more. I took a pregnancy test this afternoon and it shows not pregnant, are those test ever wrong, could I be pregnant. Can t go on menstrual cycle, because Jan was earlier than suppose to be, so we still have some time in feb. Thank you.