I would be surprised if you DID'NT think about it.

Birth control pills are a symbol of everything in your marriage - a relationship, sex and children.

So I would guess that they gave you a big reminder of your lost future together. Especially as now they are a symbol of something else - and that's someone else.

I think you will be okay - it's kind of a last adjustment to make. Adjusting to someone else sleeping with you ex is still a big thing.