Jealousy/insecure

So i always get jealous over small things. Always thinking and assuming wrong things about my husband. Its becoming a problem for our marriage. I wanna fix this about me !!

Someone recommended to me counseling or therapy .. but i dont know how to go about it?

Do i talk to my primary doctor? Or i have to look them up online ? Sorry this might be a stupid question. i just never been to a therapist before or anything like that.