It was a strange experience, not entirely unpleasant, but quite boring at times.
I feel for you, Persuader, and I say this sincerely. Some of my best friends are agnostics, and the experience was also hard on them. While a Protestant service is 98% instruction (something that’s probably easier to connect to, at least in the beginning, on an intellectual level) and 2% prayer, a Catholic service (Mass) is more like 50-50%. And, if you are agnostic or atheist, you will probably wonder, whom are these people talking to during prayer? Is there someone real “at the other end of the line”, or is it just their fantasy? Now, most of us will never have a direct sensory experience with God, in the sense that heavenly beings (Jesus Christ, angels, saints from the heaven) will not appear/talk to us in a visible/audible form. But some people, called “mystics”, will have a direct encounter with Jesus Christ or other persons from heaven (Holy Mary or some other saint, their Guardian Angel, or other angel). E.g. when Holy Mary appeared to the three children of Fatima, Portugal, in 1917, showed them the hell, where the souls of poor sinners go, and gave them a prophecy about Russia spreading her errors around the world, and causing persecution and martyrdom of the faithful, that was a mystical experience (=a direct encounter with a being from heaven, whom they saw with their eyes and heard her talking with their ears).
When entering, you were supposed to wet your fingers in a water bowl, and cross yourself. I did that (awkwardly). Afterwards it was a lot of standing up. And then down, and then up again. Apparently, they couldn’t decide what they wanted.
as far as I understood it, Catholics actually believe that the bread and wine turns into the blood and body of Christ. I have to say that I find that a bit silly.
You now what I found silly? When I was taught for the first time that a positive number multiplied with a positive number gives a positive number; a positive number multiplied with a negative number, or a negative number multiplied with a positive number, gives a negative number; and a negative number multiplied with a negative number gives a positive number. Also, when I first saw the formula for multiplying a complex number (A + Bi) with another complex number (C + Di), it didn’t make too much sense to me. And up to this day, these things seem rather odd to me. Why is there an absolute speed limit in the universe? Why 300,000 km/s? Why not 200,000 km/s, or 500,000 km/s, instead?
However, my gf was prancing about a little too smug for my liking. I think I need to take her down a notch or two (too bad sex isn’t on the table anymore).
Actually it’s good that sex isn’t on the table anymore. You are not married, you are not supposed to have sex, LOL, at least according to the Catholic rules, and your gf happens to be a Catholic. Tough luck.
When the thing was finally over, I was exhausted. At least it pleased my gf, but I don’t know if I want to do this again.
And now, think about it, do you want to do this every Sunday, for the rest of your life, if you marry your gf? On the other hand, does your gf really want to marry you if you will not do this, with her and your future children, leaving them every Sunday to do this alone?
Just doesn’t make any sense to me. I don’t know how will I survive doing this with her family for
Christmas.

Just thinking about it makes my stomach churn. God, help me! (don’t get excited, it’s just an expression)… If there is some non-believer in similar shoes, I would appreciate some advice.
On the bright side, you finally stopped having sex with her. Now you can think more rationally, and with less pressure, about what do you plan to do with your gf in the future. Marry her or not? And the rest of us, posters here, should get finally off your case and stop bashing you.
