Answer: You can assume the state of Ihram even if you are in your menses. The only thing you can’t do is the first Tawaf as soon as you reach Makkah. It means that you have to intend for Hajj only.

You remain in your Ihram until you perform all rituals of Hajj (stay in Minah, Arafat, Muzdalifa, back to Minah  and rituals during  10^th 11^th  & 12^th Dhul Hijja).

 By then if you are purified performed your Tawaf Ifader  followed by  Sa‘ee.

In case your return flight is booked and you can’t delay your Tawaf Ifader , You are allowed to do it even with your  menses , out of necessity.

You need not do the Farwell Tawaf if you are in your menses and you have to leave Makkah urgently.

It is allowed to take preventive pills as you said, just seeing a spot or two will not be considered as having menses.