My period is not yet due but I have taken my first cycle of clomid, my breasts have been tender for 6 days now, does that mean I'm pregnant?

When you are taking a new medication, one of the first things you should do is look online and drugs.com and search out your new med. For clomid, the link is
http://www.drugs.com/pro/clomid.html. There, you'll find everything you would ever want to know about Clomid and plenty of things you don't care about.
But for now, we'll start with the side effects.

Breast tenderness and enlargement are very common side effects of taking Clomid, which really stinks, because, as you know, tender breasts can also be an early pregnancy sign.

You didn't mention what day of your cycle you are on, but a good rule of thumb is that you can take a home pregnancy test 14 days after you ovulated. If you are taking Clomid, I also hope you are tracking your ovulation, either by temperature charting or urine ovulation predictor kits.

For example, in a cycle where you take clomid on days 3-5, you might ovulate on day 16 (remember, you might ovulate 2-3 days earlier or 2-3 days later). You should have intercourse on days 14,16, and 18 and then start testing no sooner than day 30.

Good luck!