Feel uncomfortable attending extracurricular work parties-do I have to go?

I work at a small company of around 20 people. The company has 2 extracurricular parties each year in which guests are invited. Pretty much everyone attends unless they have a prior obligation. Everyone at my company is married with children except for me and maybe 2 other employees. Going to these parties single I feel like the 3rd wheel or like I am intruding on all the couples there and even worry they may think I'm flirting with their husbands when I'm just being friendly to socialize. I enjoy the employee only parties but not the parties where you bring guests for this reason. Even if I was married, I still don't think I want to attend these. I find these parties forced. You are forced to socialize with other coworkers some of whom never talk to you during the work day or who weren't nice to you in the past by talking behind your back or backstabbing you. Work parties are different from regular parties with friends and family in that you have to socialize with others who may not have treated you nicely in the past. I do have a boyfriend but want to keep my private life separate from work as I don't trust some of my coworkers so don't feel comfortable bringing my boyfriend or future spouse to a work party. I also don't like my job nor feel pionate about it. I want to tell my coworkers, boss and supervisor that I appreciate the invitation but prefer the smaller parties during the work day or right after work. Does anyone else feel the same way I do? Will my coworkers respect and understand my decision not to go or will they give me a hard time for not going accusing me of being unfriendly when I'm simply not comfortable going to the larger parties? Will I get fired for not going?