I feel like an absolute loser

I am someone who's lived my entire 20s so far being in regret of my past. I've always been single, barely have had any friends and never maintained any strong friendships and I've literally NEVER been able to get a paid job ever and I finally got it at the ripe old age of 27 that I am now. Yet I STILL feel like an all-round loser and it has to do with the job I do itself. The thing is I feel like my boss is taking unfair advantage of me

I work as a PA/secretary to a Senior IT Project Manager who's a 24 year old female. The fact that this is my first ever job, yet the boss I report to is a girl 3 years younger than me just adds to the embarassment. As this is my first.ever time having any kind of job, I'm not truly aware of what I'm doing are things that are required by PAs/secretaries or not.

First of all, I completely understand my administrative tasks and have no complaints about them. However, there are other tasks she makes me do too which genuinely make me feel like Im being belittled and made to feel inferior. She often makes me shine her shoes before meetings and often makes me massage her feet at the end of a long day of work. She even doesn't aim to hide it in front of the other coworkers anymore. She even makes me go run errands for her at times like picking up her grocery, dry cleaning, driving her back home from work and even at times telling me to make late night reservations at restaurants for her and her boyfriend's dinner dates. Sometimes, when I mess up the coffee I bring her every morning she throws a fit and shouts at me to go make it again. All this while the other coworkers can hear her. 

Tell me honestly, are all these normal with being an administrative/personal assistant or secretary of someone? And most importantly how do I mentally fight through all this?