Losing hope

I had my 3rd iui and am still waiting for af to show up 🙁 I took a digital home test on day 13 in the am and it was bfp but yesterday afternoon and this morning they were both negative. I am feeling so defeated. It was such a tease. I already have two kids that are 18 months apart. My oldest I got pregnant my first iui and my second no issues. I wish I new what is wrong with me....feeling defeated