Getting fit isn't really specific enough. You say you tried cardio and weights, but those are different things, and IMO most people should be doing some of both. If you want to run 5ks, there should be a pretty straightforward path. I find weights a bit trickier, but not everyone agrees.
Start with one goal: So you want to run 5ks? What can you run now? You can't jog for 30-40 min in a row? That's fine if not. Novice runners might not even be able to do 5 min / 0.25 miles, before they burn out and have to stop.
What you do is work set times. Run / jog as much as possible, resting in between. In a few weeks you will get to 15-20 min, then indefinitely for lower paces. Try to play around with goals going for distance and watts etc. Once you get to a baseline, "I can run/jog continuously for 40min, 5km" then you can look at building distance, improving time. The Reddit /r/running sub is very good. I've been trolled by jerks, but the core community is extremely nice and supportive.
Weights are a whole different story, and in some cases excessive cardio could limit your muscle development. If you're underweight/strength you might be better off focussing on strength training, with a couple cardio workouts. Cardio doesn't have to be running, that's actually a bit of a challenging form of cardio.
However, I'm guessing most of this stuff isn't a problem, and it's more of a routine issue. There's a few things that can help. Try to view your workout as relaxing and something you WANT to do. You'll get there eventually, as it can be somewhat addicting.
Also try to bundle in with your workday. Sometime around 5-7 (morning or afternoon lol), pretend you have a meeting, or <this thing that's part of your workday>. "I can't go home I have to do this one thing". Force yourself to put one foot in front of the other and get yourself to "the place" (park, gym, ect.)... during the process try to avoid thinking that you're doing a hard thing. Imagine you're driving to the grocery store, or some fun thing.
Nutrition can be tough in that it usually requires some cooking, but this can be sped up (there's tricks which usually require sacrificing quality), and if you're very careful you can find some convenience foods. Avoid fast food, and be wary of restaurants (often much worse than fast food!). Never get the fries from fast food. If you get hungry find a healthy supplement. They sell prewashed clamshells of spinach and nutritious leafy grains (iceberg lettuce is trash, basically just water). Nutritionally it's the same, even if it's not a "real meal".
You do have to be careful as there's lots of fake health food out there. Be suspicious. At restaurants look at the portions and extras and be careful. They can hide calories places you can't see. If you're a healthy weight it's not such a big deal but its never too early to watch your sugars and fats.
I think you already know how to eat healthy. Let me list some things:
- Leafy greens
- Fruits
- Whole grain carbs
- Lean proteins
- Nuts
I suspect you already knew that eating fruits and veggies, brown rice (even some things like pasta aren't as bad as many people think, in appropriate portions), chicken, fish, and other whole foods was healthy.
Just like in the wizard of oz, you had what you needed all along! You just need to execute (though that's easier said than done).