Is it normal to have sexual fantasies about a previous partner when you are in a committed relationship with someone else?

I’ve been happily married for over 10 years and we have three kids together. When pleasuring myself, I often think of a previous partner. Is this normal? I enjoy sex with my husband but a former partner of mine was able to give me more orgasms.

I would never cheat, but is it normal to have sexual fantasies about other people? Thanks