I had similar with my pregnancy- bleeding and cramping from 6-9 weeks although mine was mostly brown only red one day. No reason found and I went on to have a normal pregnancy.
It would be stressful enough normally but in the context of long term trying to conceive, IVF and history of miscarriage it's enough to give a girl a nervous breakdown, I spent the weeks on bed rest trying to quell the anxiety, having scans helps and seeing a healthy baby, but after a day or two the panic creeps backin.

You have my sympathy as I know how scary it is and I can't give much reassurance other than to say if your baby is going well through the bleeding then it obviously isn't being affected and has every chance of staying safe and cosy.

The first trimester is sooooo long when this is happening, stay as calm as you can and best wishes for the next 6-7 months and a healthy baby xx