Are you able to visit a store nearby?
Depending on the ring itself (thickness wise) it might make a difference on how it fits even if it's a particular size.
I have a thin trinity ring in size 60, and according to my SA, a love ring should be a size down or two from the trinity ring since they are multiple rings and it overall needs to be a little larger to fit.
Turns out I needed a size UP for the thicker love ring and a size down for the wedding band love ring...
Definitely try them in store if you get a chance, and if not they make it really easy to return/exchange packages that are shipped - labels and a guide to return already included.
Happy Birthday by the way, mine is also next week and was thinking of getting the rose gold wedding band