It depends on what your normal cycle is. I used to count 28 days from the start of the last period to give me the date of the next. I don't know how early you can test as I waited 2 weeks after the day I was due on to test.
There are 28 days between these dates, so it seems you have a pretty normal cycle, with 21 days between periods. This would make your next period due around 28th Feb. The earliest you can be sure of gettign a reasonably accurate result on a pg test is the day your period is due, so there is prob little point in testing until then. Good luck!
I had a 28-30 day cycle when TTC. My fertility woman doctor said to wait until 35 days to get a definite result.. On the other hand "First Response" reckon they can detect the pregnancy hormone by the 26th day of your cycle. I'd say it's still too early to test. Good luck though - hope it's positive.