How to overcome negative thoughts

I’m struggling so bad with these bad thoughts. Intrusive thoughts I guess you can say? I’m constantly worrying and thinking of every bad scenario and thing ever...I’m terrified of losing my baby girl or family member or boyfriend the thought of it freaks me out and makes me overthink so much I want to stop thinking and worrying and fearing these things how do I manage this? I don’t want to be on meds... my daughter is almost 11 months i thought maybe it’s postpartum but I don’t believe it is because I always feared and worried of the thought of death of a loved one far before I had a baby or got pregnant.