laging may evap line

Hello po im not ttc Hi On September 27 I had my period and I had sexual deed last october 8 and I didnt have my period on the same month. (tho my last sexual deed is non penetrative just my partner rubbed my vulva/vagina usinhlg his fingers with possible semen) On November 6 I had a period tho it's light flow and only lasts for 3 days. This december 7 i also had a period, again its light flow and also lasts for 3 days. Btw, my normal cycle is 31-38 days I've been testing since the first week of november up until now (12 pt to be exact)y latest preg test was today and within the time frame po always negative result but after an hour or a couple of hours may lumalabas na evap line.. why po kaya? and diba po if ever na im pregnant dapat super linaw na ng test since its almost 10 weeks