Is it possible to be pregnant even though the urine test says negative?

I'm obese and I haven't had a period in 6 months and the last test I took was in March and it was negative. I've been scared to take another one because I don't want to be disappointed. I don't have money to go to a clinic. Everyone tells me to go to the ER and complain of stomach pains. As of right now, I cannot lay directly on my stomach. It feels very uncomfortable. I don't know what to do. Please help.