Pregnancy and TTC

Hey people I have been TTC for 3 years now  and I have been with my current boyfriend for 3 months and I think I'm pregnant but have had 2 negative tests and pain in my lower back and stomach and medium to light period like thing I got off my birth control but I don't know what's going on. I am not supposed to be bleeding for like another month or so but I am... Someone please help me... I am also gaining weight and everything. I have all the symptoms except the tests are negative...