Do YOU get my joke?

I feel bad because my sweetie has to share his birthday with Mother's Day this year. He was so sweet about it and kept saying Mother's Day trumps his birthday. On Saturday night we celebrated (if you can call it that) by going to Olive Garden for dinner and then shopping for shoes for the girls and then a trip to Target.

After church we watched a movie as a family and he cooked dinner. I love when he grills! After dinner we both split up with the kids and scrambled to wrap the presents.. some for Mom's Day and some for Dad's Bday. The cards and gifts from the kids were really thought out and appreciated.

So, he opened the card I got him and pulled out this.
And with a disgusted look, opened it and read this:
He tossed the pad to me and said-- you're gross, that's disgusting, etc... "but thanks."

(If you know Richard, you'll understand how funny he is about body function things. He likes all that stuff to be private, i.e. in 15+ years I've heard him burp maybe 3 times. He'll be mortified that I'm even posting this).

I thought it was weird how he didn't seem the least bit amused, and moreso annoyed continuing to comment about how gross I was. It wasn't until later that Tiff and I were chatting about it and he piped in, "I get it now. Okay that is funny." Tiffany and I were dying laughing not believing that he didn't get the joke until just then. What was going through his head? I mean, really, what other reason could I ever had that could possibly explain why he'd have to open a maxi-pad for his present?