Help!

I had my mirena taken out the 24th of one month, I had some bleeding on and off a couple days after, I had my regular period the next month around the 14th, the month after I slept with someone on the 12th, started my period the 14th, it was regular, I got back with my ex on the 23rd and we had intercourse multiple times throughout the end of the month, the next month I found out I was pregnant, my lmp and ultrasound directs is towards my ex, any help would be appreciated!