Late period - negative test?? Help!

Amanda • Proud Mother and Wife to my little family
Hi All,
Me and the Hubby have been TTC for a while now and in November had our first <a href="https://glowing.com/glow-fertility-program">IUI</a> which wasn't a success :( we decided to do a blind run in December with me just taking the Clomid on my own and winging it. 
For the last two weeks I've had never sore nipples (which only ever happened before when they gave me the HCG shot for the <a href="https://glowing.com/glow-fertility-program">IUI</a>) , I had a couple random bouts of "bathroom issues", and I've been more fatigued than normal. 
Anyways, I decided not to get hopeful since the chances of on our own are very small. My period is now 4 days late. I took a test on the first day and it came back negative. For the last two days I've had very minimal spotting... Like, very light pink and only if I'm checking my cervix (wiping shows nothing).
Called my doctor, she wants me to do blood work...but I've also been crampy randomly for the last few days that I keep thinking AF is going to be here any minute.
Has this happened to anyone else??? How long should I wait before doing a blood test? I don't want to get too hopeful, but I'm not sure what the difference is between spotting and implantation bleeding...
Anyone have any similar stories?!