Am I pregnant? HELP!!?

My period was irregular for the most of my teen years, now I'm soon to be 22 years old and my period seems to be regular now on about an average of 28 days. By irregularity, I tend to have frequent periods like 2 times in one month or 1 time in one month. All I know is that I always have my period at the last 2 weeks of every months. My last period was on June 1, 2011. I am supposed to be expecting a period sometime this week and I know when I am about to have my period, I would have sore breasts, bloating, and cramp before I actually get my period. I have none of that yet. I just got a little bit sick last Tuesday in the evening out of blue and felt like I want to throw up. I was trying to refrain myself from vomiting until it passed about half hour later. I felt a little bit of cramp but not period-like cramp and fluttering. Before that, I kept noticing that I have very wet clear discharge on my underwear that I had to use pantiliner to absorb the fluid few days before I felt sick. I had dull headache, I went to bathroom little bit more frequently than before. It could be the water that I've been drinking. I did some researches about pregnancy and some of the symptoms fit me but I'm afraid that it could be something else. My boyfriend and I had sex every weekends for an entire month so far. We had been careful with condoms and few unprotected sex (withdrawal prior to ejactulating). I still feel like something is doing something in my belly. It's highly unusual to me. I don't have sore breast and I am about 2 days late! Usually when I'm about to have period, I start off with brown discharge but NO period so far. I never gone on without having period that long. I'm concerned that I could be possibly pregnant. Am I pregnant? I am planning on taking a pregnancy test this Friday so is it too early to take the test or should I wait a little bit longer? I value your opinions. Thanks!