I've been working out with weights for months now and i dont know what its called but i suppose my conditioning... or... ability to handle more (more work.. not more weight) hasn't improved at ALL.

I mean i feel absolutely dead (sometimes even nauseaus) from even a few sets of chest flyes and curls and totally drained after... after a set or 2 of a bigger exercise such as weighted lunges/squats i am totally 100% drained for basically the whole session...

Is this a low level or aerobic fitness or what?

Yeah, could be. Do you make sure to breathe deeply during your lifts? Also, are you eating properly, getting enough sleep, and do you have enough rest days during the week?

Whenever I feel like this, I take three days or so off from the gym, and then come back to it. I usually wind up feeling a ton better and able to hit it hard again.

Everything that Evan said + make sure you're not doing too much work in your routine. You might be overtraining.

How often are you training with weights?
How frequently does each muscle group get worked?
What sort of rep/set scheme are you using?

How much sleep are you getting at night??
How good is your eating regimen??

I would just like to add. I had a similar problem, I was eating right and healthy, I wasn't doing too much volume in the gym so I wasn't overtraining but I was still feeling this awful fatigue every day. I was feeling very sluggish.
Insufficient sleep was the problem in my case. I was sleeping around 6 hours daily. Now I sleep 8-9 hours. I was suprised what kind of difference could just a couple of hours of sleep make. Now I feel very energetic and alive.

Educated guess - you're not eating enough and probably eating the wrong things. Cut out as much refined sugar as you can from your diet and track your calories to ensure you're eating enough to support muscle growth

Check your diet and the amount of cardio you do.

Must be the diet i think.

I get minimimum 8hrs sleep / night, usually more.

I am definitely not overtraining trust me! i have plenty of rest days and my volume is tiny.

Sounds like diet man. What does your diet look like ? Maybe you should up the carbs, and what do you eat fore pre-workout?

While diet is a good bet, I'm curious abut the details of your actual training here. How much you are lifting is about intensity. It's about sets/reps, weight, and rest in between.

If you're unable to complete the work-out without getting sick or being totally drained, it would suggest that you're trying to do too much with that session. If your sets/reps amounts are manageable, then maybe the actual weight amounts are still too much. Or maybe your rest in between sets is not enough.

Do you drink water before, during, and after you workout?