So frustrated

I have 2 children which I am extremely thankful for & I feel so blessed. My husband & I have been trying for 3-4 months for a third & it's just not happening. I don't understand what the problem is. When I was 17 & on the pill I got pregnant with my son. When I was 24 I got pregnant with my daughter after trying for 2 weeks. Now it's just not happening and I don't know why. I'm worried my IUD may have messed something up. I had it for less than a year & got it out almost 5 months ago. I had a chemical pregnancy last month & that was so devastating. I know I'm not the only one going through this I just needed to get it out. Thanks to anyone who listened & if anyone is going through something similar I'd love to hear your story.