Missed period, could it be pregnancy ?

I am an over-weight female who had already missed 2 of my periods and i was just wondering how am i suppose to tell besides the symptoms(which i have almost every one of them) if im by chance pregnant. my mother has told me that it could just all be in my head.. the sypmtoms and the fact that i could be pregnant. Me being over-weight has brought down my hopes of even getting pregnant and i just need to know what or IF there is anything i can do to tell. My boyfriend has urged me to get a test just to see but the negativity factor of the test has me kinda worried about it and how i might tell my boyfriend that we might not be able to have children. I have the main symptoms of pregnancy and everything i just believe that i cant get pregnant but deep down it almost feels as if im already pregnant and i do believe i sound like a 13-year old virgin saying that. but i am 20 years of age and my boyfriend and i have sex atleast 2-4 times a week with no protection or contraception.. Any opinions or advice on this would be great. and im talking more than just "go get a test"
Thanks