How to get rid of them?

I just recently move in with my now husband and i found one bedbug! I was sitting on the couch and felt something on my head then i shake and felt it on my hand and saw a black/brown bug the size of a bedbug. I told him about it and he keep saying there is no bedbugs there and that it was so rude to say! Right now I’m pregnant with twins and had to move back with my mom this week, my reasons were bcz i wanted to relax good in this last week (c-section July29) So i found a bedbug here now at my mom’s and trust me, there was never bedbugs here at her house. So I’m afraid i carried that on my clothes from my husband’s house. He has three kids (12,9,5 yrs old) and their room is a complete mess! So im afraid his kids are the ones who carry those bugs from their mom’s house.