The singer made the troubling revelation over the weekend while performing in Belgium, where she continues on her mountain of a tour. She's got a dozen more stops across 15 different countries -- that's the plan, anyway -- but, in her own words, the Material Girl's simply not feeling great.

Madonna said this in the context of discussing her health scare earlier this year -- which saw her in the ICU for a time, fighting for her life after a bacterial infection -- something she says she's thankful to have survived ... while in the same breath, reminiscing on her late mother.

Madonna says it's a miracle she came out on the other side of that ordeal, but folks online focused on her words about how she's feeling right now .. which sounds iffy, at best.

Strangely enough, Madonna was drinking onstage out of what looked like a beer bottle ... and like we said, she finished the show -- not to mention a string of London performances she did last week to kick off this international tour. So, on its face, she appears okay enough to get through it.

Still, people are weighing in, expressing their collective hope she's getting the proper health care she needs -- and more importantly, sound medical advice.

The sentiment from her fans here is ... don't force yourself to do this if you're struggling, 'cause we'll love you anyway. Remember, this tour was postponed for a good long while this summer as Madonna battled her infection, and she seemed set on seeing it through.