Sexual Harassment

I am a 20 year old male, and have been working at a doctor’s office now for two years. I can certainly say I am a "jack of all trades" The manager (who is 60 and female) there seems to be a little "too friendly". On a daily basis she will call me "sweetie". That obviously doesn't seem all that bad but she will often run her hands through my hair, rub/tickle my back. The manager literally lives next door to the office; I mean its only 25 feet away. On one occasion I went to her house right when work got out, with another co-worker because she got a new puppy, our manager greeted us at the door in a tuxedo shirt and underwear. On another occasion the manager and I had to go to a meeting and I offered to drive, I was to arrive at her house at 7:15. I am usually early for everything and from I got there at 7:10. Here she greeted me in a night gown and said "oh, your early", too me I didn't think I was all that early and felt it was inappropriate for her to answer the door in that manner. Also from time to time she has asked me to come over and help her with her computer. During these visits she has asked me if I would like a beer. (I am only 20, but the first time she offered I was only 19). There was also another time where our computer system at the office was due for an update; she wanted me to stay there with her to help get all of the computers set-up. While we waited for our tech company to set-up the download for the servers she suggested that we go over to her house and relax, watch some T.V. She went and got her self a beer, and offered me one, I turned it down. (We were both on clock). I find it very inappropriate to offer a minor alcohol especially while on the clock. Now all of this I really don't have proof of, with the exception of the co-worker who witnessed her in her underwear, but I know this co-worker would never go against our manager. What can I Do? Also I frequently go to Wal-Mart and such stores to get office supplies, or what ever the situation may be, and they always make me punch out, and never pay me mileage. I know that by me punched out than they don’t have to pay, but if I refused I know they would let me go. I am sure my best bet is to quit and leave this all behind me, its just this job is a great opportunity, and I get along with almost everyone else. I don’t feel this is fair to me. I truly don’t have anyone to complain to as she is the manager, the only one left is the doctor who owns the office, and I know he would never believe any of this. Previous to this manager, the position was held by her niece, and previous to that, it was her sister. The owner/doctor loves her family. Again, what can I do?