I am 8 days post iui. I have had 5 diff brands of home pregnancy test come up very positive even dig test. I went for a beta hcg today and my level was only a 4. My questing is how can hot show me a positive with that little hcg in my system and is there any
Chance my test could be wrong or my numbers could still go up

Yes it is possible, wait a few weeks and get checked again.