TTC and after 18 months maybe successful...!

My boyfriend and I have been TTC for eighteen months now. We haven't told anyone (apart from my sister who already has kids). I'm 28, and during this time of TTC at least five friends of mine have all become pregnant, all without trying and seemingly effortlessly. It's really tough when you can't tell them your trying too, especially as you don't want to rain on their parade as such, I just put a big grin on my face and congratulate them. I was beginning to think either I or my partner are infertile... but... my AF is now 7 days late, and has never happened in my regular 26/27 day cycle (I'm on day 33 now). I've been sick every day for a week and my breasts are swollen and so very painful. I'm nipping to the pharmacy now to get a HPT but am very scared that it will be negative! I have to know though, otherwise there is something else that is causing this horrible queasy sickness!!
Wish me luck!!