Am I overtraining?

I've been working out regularly since early 2006, when I finally got fed-up enough about being fat to do something about it. I lost about 50 lbs. and have been able to keep it off (currently struggling with a marriage-induced gain of about 5 lbs., on account of frozen pizza, buffalo wings, burgers, and beer).

Anyway....

My current routine consists of going to the YMCA about 4-5 days a week, where I bust my ass on the elliptical or treadmill for 30-45 minutes and then lift weights for 20-30 minutes. I routinely get my heart rate into the high 170s-upper 180s on the elliptical (from a resting heart rate of 50-55 bpm) and sustain that level of exertion for 15-20 minutes; the remainder of the cardio workout is spent with the heart rate in the 140s-150s. Occasionally, I switch up my routine by riding the bike or jogging on the treadmill, thought both are rough on my knees. As far as the weight training goes, I've always been able to lift a considerable amount for a woman (I have to laugh when the magazine recommend using 5-8 lb. weights, since I use up to 25 lbs. depending on the exercise). I don't have a steady weight training routine, but my only guideline is to work antagonistic muscle groups on the same day (e.g., biceps and triceps, chest and back, hams and quads) and not to do the same thing two days in a row.

Here's my problem....

I hit 150 lbs. and the scale doesn't so much as twitch in the lower direction. The lowest I had gotten to was 146, but it quickly went back up. As I mentioned above, I've gained about 5 lbs. in the past ~4 months. It doesn't seem like much, but it's enough to annoy me. Since I know what caused it (enjoying life), I'm confident that I'll be able to shed the weight. But I know from experience that the number will refuse to drop any lower. I'd like to lose at least another 5-10 lbs. beyond that, but in spite of my vigorous workout routine, nothing seems to happen. That's why I wonder -- am I overtraining? Is my body trying hard to hang onto all my fat? I read somewhere that overtraining causes fat to be deposited in the lower abdomen (one of my trouble spots) because of excessive cortisol released into the bloodstream, and the more a person tries to exercise off that pooch, the more the body is stressed, and the more cortisol is released. So, it's a vicious cycle of attempted gunch-removal leading to gunch-retention.

But then you might inquire about my eating habits. For breakfast, I usually have a David's whole-grain bagel with "natural" peanut butter (i.e., that which is made from peanuts and oil, not partially hydrogenated crap) and organic jam; when I get bagel fatigue, I'll have oatmeal with brown sugar and dates, Grape Nuts flakes with almondmilk, or rarely, scrambled eggs. For lunch, I usually have leftovers from the previous night's dinner. Dinner can be a wide variety of things, ranging from salmon and corn chowder to wild rice casserole to homemade Chinese food to tacos to.... you get the picture. Everything I cook is from scratch (except things like bagels) and often includes organic produce and dairy. For snacks, I try to have fruit, beef jerky, pickles, etc., though I do like Chex Mix and granola bars and the like. I don't drink pop and I don't use artificial sweeteners, except for stevia. I have an affinity for desserts, but I do try to limit them as much as possible. I realize that if I cut them from my diet entirely, I'll crave them more. So, I'll have a little bit of chocolate or candy every now and then, which ends up being just about every day. I will admit that I overeat every time my husband and I go out to eat -- when we go to Perkins, we both clear our plates; at other restaurants, we both gorge ourselves on pizza and chicken wings and burgers. One time, we went to Red Lobster (before we discovered Darden Group supports seal culling, but that's another topic for another post) and my husband inhaled almost 60 shrimp in the all-you-can-eat special while I had a lobster tail, 5 large shrimp, 4 scallops, about a cup of rice, a Cheddar Bay biscuit, and a Bahama Mama cocktail (ouch. it's a little painful to recall all that). I eat out more and drink more now than I did before we were married, but I know that's the cause of my RECENT 5lb. gain.

My wonder is this -- why did I hit the 150 lb. plateau and have been unable to get the number any lower? Does anyone have any suggestions?