I take Loratadine daily because of my asthma (triggered by allergies) and my GP said it was fine to take while ttc or pregnant. If you search Antihistamines while pregnant and click on the NHS link and scroll down there's a section about taking it during pregnancy. I hope this helps. X
I felt the exact same, it's really weird how it randomly started after transfer. Hopefully it's a good sign? Hope it gets better and good luck for the 2ww x