I need some guidance

I am 5'4 and 193 lbs.  I have been doing spin class 4 days a week at 50 min. a session.  I also do some toning and stretching exercises.  I don't claim to be an angel every time I eat, but I don't eat bad either.  I have not lost any weight.  Even my doctor decided to test my thyroid because he said I was definetly active enough.  Well, my thyroid is fine and he seems to be done worrying about it.  I just don't understand how I can keep exercising like I am and not lose something.  Does any one have any ideas or suggestions?

how much are you eating? not suggesting you are eating too much -- but probably too little

Did you take body measurements when you started?  do your clothes fit the same?

It sounds like food is the issue here.  You need to do a food log, and write down everything you eat for a day and start calculating how much protein, fat, carbs, etc. you're consuming.  Try eating a small meal every three hours, and you also need to be drinking plenty of water.  I agree with the post above as well.  Have you had any before and after measurements taken?  Sometimes you don't feel like you lost weight but you may have lost a couple inches.  I would suggest taking a yoga or pilates class as well.  You won't sweat a lot, however they tone your muscles and actually help you drop inches very quickly. 

You have to challenege yourself, and push hard.  Make a goal to burn 600 calories when you're at the gym, the point is to set realistic goals, and make them. 

Yeah I agree with what the others wrote... A few years back, I managed to gain 20 lbs and keep them ON while teaching high-impact aerobics classes (like body boot camp) 5 days a week.

I guess I thought I could eat whatever, as long as it wasn't "junk," and I'd be okay.  It turns out I was really underestimating my caloric/fat intake, and preventing any loss.

I would try logging your food for a week, and see if you notice any changes.  I also agree that you should take measurements, they can be really encouraging :)

You could also work weights into your routine 2-3 days a week...  Great job sticking with your workout routine!

I think you will see the results soon. I walked two miles a day for three weeks, plus jazzercise two days a week. I saw the weight come off only after a month. When it did come off I noticed that I was toned all over. This has happened to me twice where the weight came off after a few weeks. Keep up the pace and it will soon pay off

I started out with your stats (5'4", 190lbs) in January.  Now I'm down to 165 (everything slowly, but surely).  From January until April I worked out 7 days a week (cardio) and 3 days of weight lifting (which I really think is the key to my weight loss.  It motivates me because I love feeling my muscles!).  Plus making sure I ate between 1800-2000 calories a day.  I also track my body measurements because even if the scale isn't moving very much, my measurements usually go down.  You can do it.  My personal mantra is the weight didn't pile on overnight, so it isn't going to leave overnight.