Lmp august 4th. unprotected sex aug 21. cycles usually 26-28 days. i got a positive just before i turned 3 weeks (if i did the math right cause this wasn't planned) hcg levels seem to be rising. i keep doing tests. is this a good sign ?

No: No, it is not a good sign if a person "keeps doing tests." Women only need one pregnancy test (or sometimes none), if it is positive. Nature's other signs of pregnancy follow a typical course, well known to women and their doctors. Thus, the question is, "Why is a person doing multiple tests?" One's doctor can interview the patient to find out why, and to see if the reason is a cause for concern.

Too soon to know: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.