I've had more side-effects from OCP this, my 2nd round of IVF - certainly more nausea, tiredness and bloating. I am on microgynon also, the same as last time, and same dosage.
I'm thinking it might have something to do with being on another stim cycle relatively soon after going through my last one - I am doing back to back. Maybe the body is simply dealing with being on another forced set of hormone changes so soon after the last lot of stims.... how long ago was your first IVF cycle? Was it recent?

Also, on a par with slyder, is the dosage larger this time round? I know there are two doses used typically with microgynon in IVF - 20mcg and 30mcg. Maybe your dosage is different this time?

In any case, it might be a little early to be doing HPTs at CD 20 - can you speak to your clinic about the side-effects?