cooling problems, need help!

I have an E36, I watched the video on cooling system bleeding and did exactly what was done in the video but I'm still having issues. First off I constantly get the check cooling warning light but the car never overheats. I'll add some fluid to the fill line in the tank but a few days later it will be below the line again.*
Today I tried bleeding the system again and noticed my fan is constantly running and I get mediocre warm air when I crank the heat all the way up. Could my*thermostat*be bad or what issues could cause this? Thanks for the help guys

Matt**

cooling problems, need help!