According to the following link, it is unsafe during last 3 months of pregnancy. https://us.hisamitsu/pain-relief-faqs However, I think is better to avoid though you are 5 weeks now. Better to avoid medicated plasters and certain oil during pregnancy. You may want to try celery and cucumber juice and drink plenty of fluids for your migraine. Take care.
Avoid using any medicated plaster while pregnant. Ingredients are not safe for pregnant women. Use hot/cold compressor instead
Mrs. Ho