Is it normal to get hard when i'm around my mom

Hi everybody just wondering if anybody els gets hard in the presents of their mother. My mom has been divorced 3 years now. Recently I've been getting really hard when she talks to me. Yesterday she was putting the dog out on a leash. She bent over and I seen her pink snatch underneath her night shirt. I got so hard I could barley hold back. I went to my room and masturbated to the sexy thought of rubbing my face right into that cute pussy. I recently have been smelling her dirty underware when I masturbate. I rub one pair around my c*ck and the other dirtiest pair in my face. My mom is a heavy set women with huge boobs, ever since the divorce my mom has been wearing tighter cloths, showing off her beatiful fat body. She recently started smoking vs 120's. I have a huge smoking fetish and this just blows my top, enough to put me over the edge. You have no clue how bad I want to stick my d*** in my mommy. When she drives me to school she smokes at lease two smokes on the way. She leaves her window down a inch and some of the smoke drifts over my way and I get sooo hard. I always leave the car in the morning with a huge boner. Than its straight to the bathroom to touch my self thinking about my sexy mom. It doesn't end there, I love to masturbate in my moms bed and cum in her sheets. After I cum I feel so ashamed of my actions, but when I get horney again I forget that feeling. I've always been attracted to bigger girls so I think when she started showing off her body thats when I started feeling this way. The smoking just made me want her more.....