Very light early period and cramps.

I am on my TTC journey. Last month my doctor advised me to start taking fertomid 50 mg from cycle day 4 for 5 days and start follicular study from cycle day 10. I could not follow this treatment due to travelling so decided to give it a go this month. I was supposed to have my period on 14th April as per the app I use but I got it two days early on 12th April. So the previous cycle was 27 days. It was a very light period with hardly any bleeding but I had period like cramps on the first day. There was little to no bleeding for three days. I took at home pregnancy test thinking it could be implantation bleeding but it was negative. Today is cycle day 6 for me and I want to start fertomid and go through the advised treatment. Would there be a problem in case I am pregnant and end up taking fertomid for next 5 days? Please advise.