TTC with a new partner baby number 3

Im 29 and have and 7 and 5 year old girl with my ex husband. My eldest was an <a href="https://glowing.com/glow-fertility-program">IUI</a> pregnancy ( due to husbands low sperm count) and my 5 year old a narural conception - which was a total surprise as i never thought I could fall naturally with my husband.

I am now happily engaged to my new partner and have been TTC for 6 months with no luck.

Im starting to get the same disheartening feelings I had many years ago when I was trying for my first daughter for 2 years with no luck.

My fiance has a 5 yr old daugter who was conceived naturally after only 2 months of trying with his ex.

I dont know whether to try <a href="https://glowing.com/glow-fertility-program">IUI</a> again or continue to go on trying naturally as we are?