RIGHT!!!  My description has been edited to say what was intended. In my defence, it has been about 47 years since I had s slipping Mini clutch! I would sense it slipping in 4th going up hills and have to downshift. (Maybe I should have let the morning coffee fully soak in first!)

Dan and Ken, he said slipping in upper gears, your comments imply the opposite

+1 - what Dan said.

Thank you my friend. Its going in and out of gear without issue, but when already in gear its slipping in all gears. This problem literally just started a week or so ago, almost wondering if somehow my fluids in transmission are low.? Putting her in the air tomorrow after work. Any advice will be appreciated, and I'll keep updated with what I find tomorrow 
  

You need to say what era your Mini (classic) or MINI (BMW) is.

The symptoms suggest to me a badly worn clutch disk. When it gets worn, the pressure plate is no longer capable of pressing it tightly to the flywheel, so it slips. It is more obvious in higher gears because the engine and clutch have less mechanical advantage. In 1st gear, the engine's mechanical advantage is highest and you don't notice slippage, but it will eventually.
Time for a new clutch. Don't delay or you may glaze or scar the pressure plate and flywheel, if it hasn't happened already.

I'm new to the mini family and absolutely love my adult go cart . I've owned her all of three months now and here recently she wants to slip in all but first gear after reaching 2500+rpm. The clutch is engaging and disengaging properly so I'm a little confused on what may be the issue. I usually turn my own wrenches so any help would be greatly appreciated