two week wait nervousness

I am currently in the second part of the tww and I'm starting to get very nervous and down. My husband and I have been married for 7 years (I'm 33 and he is 41) and we have been trying for two and a half years. In that time frame we got pregnant twice. I had a mc at 7 weeks in 2014 and a chemical last summer. We moved on to IUI and just completed out 3rd. Each time my husband had a great count and I had a couple of mature follicles. I don't understand why it isn't working. Every test we could do came back normal. Just very sad. It's the hardest thing I've ever been through. My RE is recommending IVF if this 3rd IUI fails...