Spotting Early with twins

I am a first time Momma and we just found out on Thursday that we are expecting twins. 5 weeks 5 days. Twin A is doing exceptionally well and Twin Bs heartrate was a bit lower. We were told to be optimistic but it is possible it wont make it. I am a plus size girl and this pregnancy is a result of 5+ years of ttc and our 3rd IUI. I had implantation bleeding and then a couple weeks later I had spotting after intercourse. I had a transvaginal ultrasound on Thursday but I don't think its related to the spotting I had this morning. It was heavier than the last two but no tissue or clots and not bright red. Its very similiar to the last day of the cleanup phase of a period. Im wondering if this is normal and is it more common with twins? Hoping someone can ease my mind. Im waiting to hear back from my dr today.