Should I marry him or are just wait for another man??

LOVE • 2018 new year's resolutions......
I'm 29 yrs old,still single.I've never had sex.but I met with my fiance 1 yr ago we've been in a relationship and soon planning to marry,,,but he had one kid with his ex,whom they have divorced for 4 yrs now...tho his ex is the one who decided to walk way and took her kid with her leaving my now fiancee desperately,,I know he told me all his truth abt his previous marriage but sometimes I feel insecure coz I keep thinking what if they one day decides to get back together?