Fantasising about a co worker

For the last couple of months I have been fantasising about a co-worker and masturbated to him once but yesterday when my boyfriend was playing with me I didn’t feel the run up to orgasm but once I thought of my co-worker it came straight away, We never flirt full on at work but we work closely together every day and there’s the odd innuendo thrown in every now and then. I would never act on these feelings I just want to know if this is normal, google only came up with answers from blokes so wanted to know what you ladies thought.