I'd suggest that you try ANYTHING for 20-30 minutes a day. What kind of exercise do you like? What are you looking to do or learn?

Well I'm not a huge fan of exercise really. When I'm at the gym I usually use cross trainers, rowing machines, bikes and weight machines. At home I try to do sit ups and some stretches everyday and weight training every other day. I hate running so that's out of the picture! I like walking, but I'd prefer to do something at home or at the gym.

OK. Let's get real particular here. What is the exact goal that you're looking to achieve? Increasing overall fitness is too vague. Do you want to lose weight? Do you want to change your figure? Do you want to exercise regularly? ... it sounds like you're almost ready to stop before you start. Having a goal keeps you motivated and on focus. So --- what do you REALLY want?

I hate running too.

Any kind of cardio will help with your problem. Bikes, swimming, stair steppers... just anything where you are moving enough to get your heart rate up for 20 minutes.

A gym usually has cycles or machines you can hop on and do cardio. Some even have specific workouts programmed into them that could really help since doing just a flat pace.

If you don't want to do cardio everday then maybe switch it so you do your regular weight workout Monday, Wednesday, Friday and then just cardio (and maybe abs) on Tuesday, Thursday and even Saturday.

To help motivate, you could try signing up for a class.

I wouldn't mind losing a bit of weight, but not loads, maybe just a few lbs. I don't want to change my actual body shape because I really like it. By fitness I meant to make my heart stronger, because I often get a high heart rate when exercising (up to 190 bpm) and my resting HR is below average. I want to know what exercises I can do or machines I can use to make it stronger and therefore give me a lower HR, because what I'm doing at the minute doesn't seem to be working.

I said I don't really like exercise, but I'll still do it. I like the feeling after a good gym session, where I feel really fit, and then it seems to disappear as soon as I eat lol.
It's hard to explain, I just want to lower my HR cuz when it reaches 190 bpm even though I'm not going super fast it gets me kinda worried lol.

Well, try doing a warm up so you can ease into things a little more.

How quickly your heart rate goes up doesn't really signify poor fitness, it more points to how hard you are working. Focus more on your recovery time-- the shorter that is, the more "in shape" you are. So how long it takes you to get from your target heart rate, back to resting again.

Do you work out at a flat pace (constant speed) or do you switch it up at all?

I'd suggest that you consult a fitness coach with your goals and request that she design you a specialized series of exercises using machines and maybe even classes they offer at the gym. This way, you can have a plan of action. But you NEED expert help and these concerns can be addressed to an expert in Fitness. What gym do you go to?