vaginapagina | at home pregnancy test reliability

alright.
i'm new to this and i'm kind of stressing out but heres my situation:

well basically, my best friend hasn't had her period for roughly... 3 months. she got her period, it went away, she had unprotected sex, and then i think she said she got her period for 2 days and thats it since then. now, she said she came off birthcontrol awhile ago and came off it cold turkey, just stopped taking the pills - and her doctor said a funky period could be result of this. but she is too afraid to ask her docter about it right now.

we got the EPT test that says pregnant or not pregnant and the first one came out NOT PREGNANT so thank god but we are still sketchy because she freaked out today cause she noticed that her nipples were HUGE compared to usual.

now for my questions:
i did some research and large nipples can be from infection.. which could come from some sort of heat. she has a heat rash on her chest, is there a chance this could be the same thing?

and also, i tried looking at peeonastick.com for personal stories on the EPT test with the pregnant/not pregnant thing but i didn't really understand what i was looking at. do you guys think these are accurate? or do you know of a test that is more accurate.

is it more accurate to get tested at a clinic? and does it cost money?

blah. so stressed. she really freaked out because she isn't showing at all in any other way but if she was i think its like a figment of our imagination. i don't know. shes 18, in pretty good shape - very active. what are the chances a test would say she isn't pregnant even if she was?