If you are exercising and your body is not changing then you are either not eating enough, you are eating the wrong things, or you are over-training your body (and not giving it enough time to recover).
The saying goes that if you are not seeing progress you are either "a wimp in the gym or a wimp in the kitchen."
People have told you to eat more. Specifically, you need to find out what your Basal Metabolic Rate (BMR) is. Once you know how many calories you need for your age, height, weight and activity level to maintain your current size, add 500 calories per day. This puts you at a 3500 calorie surplus per week, which equals one pound gained per week (on average).
Use this to calculate your BMR and then your Harris Benedict:
Harris Benedict Equation
You will need to work out an eating plan to get your calories. You will need the right combination of proteins/carbs/fats to grow. Google will be your friend in figuring it all out. Eating them in the wrong ratio will put more fat on you than muscle.
Then, you will need to choose a good exercise program. Monitor your lean muscle versus fat gain by examining your body fat percentage about once per month and adjust diet accordingly.
Lifting heavy shit + eating right + rest = getting huge (I used to be 175, now at 202).
Supplements like creatine will do nothing for you if you are not lifting right and eating enough (enough being more than you need to).
Also - people have told you that cardio will limit gains. A few key points:
Before you run or lift, you need to have a lot of complex carbs (from brown pasta, oatmeal, bismati rice) in your system so that you body will use carbs for fuel instead of protein.
If you run in the morning, first thing, you can get away with no carbs as this will force your body to burn fat, but I would not chance it.
Another thing you can do it eat heavier on your heavy exercise days to offset the caloric deficit created by running.
Oh, and keep a log of everything you eat and do (exercise wise). Google Calorie or nutrition counters for help. There are also free sites to help you do this.
This is called Delayed Onset Muscle Soreness and is natural.
Sorry for my rambling. I felt like I kept forgetting something.
Good luck.