Why does breastfeeding make me feel weird?

This might sound stupid but when my wife is nursing our 5-month-old I sometimes feel jealous? Like she has this bond with him that I can't replicate. I try to be supportive and get him ready for feeds and I do nights with pumped bottles, but there's something about watching them together that makes me feel left out. My wife says I'm being silly but it's real. Anyone else experienced this or am I just being a jerk?