Help!!

Michelle
So, I had my IUD (Mirena) taken out Feburary 5, 2015. I didn't have a period for the 18 months I had my IUD. I bled from the 8th of Feburary to the 12th. Then I didn't bleed again until March 14th to the 21st. We have had sex almost everyday since March 18th. Sometimes twice a day. We are TTC! Well, yesterday I started bleeding again. Only this time it's different. I have no cramping, but I am nauseated! At first the blood was a watery thin fluid, now it's a dark red / brown color and a little heavier. On one app I was supposed to start my period this month on the 11th and others not until the 17th.  I have taken 2 - 3 pregnancy tests in the last week and all negative. What is going on? Is it me or could it my husband? I should be pregnant because we have been having sex a lot.... Like I said sometimes 2 times a day. :-(