What Causes Decrease In Blood Flow During Periods?

Question: Hi, I am on ginette 35 for 10 months. My last month period was on 18th march. i started the pill on 20th march and took it for 21 days. but on 25th march i was involved in a sexual activity. my partner touched his penis and then put it in me directly, though it wasnt erect when he touched it, i am scared something might have gone in. It was very rigourous fingering and i bled after that for 2 days. (spotting). I got a quantitative blood test done for pregnancy on 9th april( 6 days before next period). It was negative. My last pill of ginette 35 was on 9th april as well. I got my period on 15th april as expected but the flow was very less. I needed tampons but usually bleed for 7-8days with heavy flow for atleast 3-4 days. Could this mean im pregnant or just that ginette 35 worked, I am also very stressed , could that be a reason? i jumped a lot without to get more flow, stupid me! and without a bra and hence have sore breasts, but since its a symptom, i have back pain and leg cramps as well ( may b because of the jumping). Please help me, im very anxious

I started the pill on 20th but missed 2 pills on 21st and 23rd march...but after that took all the pills... I have stomach cramps after the flow has stopped...I usually have it before or after the flow...I have been diagnosed wid low vit b12 and iron deficiency. I feel very tired these days. Could dis be bcoz of the deficiency?? I will be able to take a blood test in may 1st week only..so the result will be completely accurate that time??

When can sonography tell if I'm pregnant or not?? And can blood test give a false negative at all?? I will be doing a urine and blood test as well but want to do a sonography to be very sure... And the bleeding g after the sexual activity is it normal? And I had strings of brown blood for 1-2 days on 6-7 the april...very very lil amount...could that be implantation bleeding?? And my flow was very high till last month ...can flow decrease so much in 1 cycle??