Toilets, Sinks, Showers, Tubs and Disposals - toilet troubles

Hi, I'm having problems with my basement toilet and possibly tub. Lately, sometimes my toilet flushes really slowly or not at all. It just fills up and swirls around a bit, and then the water level drops to normal, or sometimes the water will almost completely empty the bowl. Last week, some of the waste from the toilet came up through the basement tub in the same bathroom. I did a bunch of plunging which I think helped because the toilet would finally flush normally, but after a few uses, it would start to flush slowly again.
I think it stopped coming up through the tub, but I have noticed when I plunge the toilet, some water comes (not much) comes up through the tub, still.

I have plunge the toilet numerous times and have even used a 6' toilet auger. But I'm still having this issue. Seems like it will be okay after it sits for a while - after it sits for a couple of hours or so, I can get a good flush, but then after a few more flushes it goes back to just swirling around the bowl.

I'm wondering if I need to snake the tub?? Or remove the toilet and snake from there.

I've been in this house for several years and have never had any plumbing problems. Oh, and I'm not having any problems in any other areas of the house.

Any help would be greatly appreciated.

You have a clog in the main line downstream of the toilet, this has to be rodded out, I think that you have to snake from the toilet, plungers will not work, luck.

Snaking from the toilet would be best option. :)

Thanks for everyone's response.

Turns out is was the sewer ejector pump. I failed to mention that there was some leakage coming from the sewer tank in the basement closet. My pumber friend came by and replaced the pump. All is well now.

Thanks again!!