Sparkplug, please forgive yourself for being a human being, and female. For myself (female), I do cry when I'm stressed. It's something I can't control, the tears just come out! Fear, as well as anger and frustration create a TON of stress, and tears, too. So the f'ing corporate world wants us to be robots - or act like men who, unfortunately, we as a society have taught to suppress, suppress, suppress those emotions and natural reactions.
Fear, happiness, love, hate, anger, and the real killer, stress, have effects on our bodies and cause the release of - well, I'm not sure what to call them because I'm sure no physiologist, hormones? chemicals? - into the blood stream that cause the body to prepare for the classic "flight or fight" response. In our 21st century, however, we find ourselves confronting the fight or flight response in "inappropriate" circumstances, such as having to deal with an obnoxious workmate, foul-mouthed, loud teenagers on public transportation, a jerk for a boss, etc. etc. Oh my goodness, how many times I've just wanted to stand up and scream at the top of my lungs, SHUT THE F' UP, JUST SHUT THE F' UP, I'VE HAD A HARD DAY AT THE OFFICE AND ALL I WANT ARE PEACE AND QUITE, YOU STUPID, PATHETIC LITTLE NUMBNUTS or GET OUT OF MY WAY, YOU A-HOLE OR I WILL RIP YOUR HEAD OFF AND STUFF IT UP YOUR ***. And ahhhh, imagine myself as Michael Douglas with a gun, or Rambo with a knife...
Geez, sometimes I scare myself! Do I have a solution? Humor (the internal kind), has helped me. At least, I haven't killed anyone (yet). There seems to be a conglomeration of issues involving hormones, acculturation and socialization, and things learned over a lifetime since coming out of the womb are not so easily overcome. But, at least with this "problem" (I do not see crying when under stress as a problem, but other people do), I believe there some techniques that will help you control the stress levels and perhaps prevent those welling tears from overflowing - at least, until you get home. I find imagining myself as Rambo "getting even" works really well, particulary when I do it while I'm being reamed out or blown off by an inferior being who happens to be my "superior" at the office. And, someday, I just may stand up on the bus and, screaming at the top of my lungs as I charge toward the back seats where the snotty kids sit, stop just short of nose length from the biggest and stuppidest looking one and say, in a fake British accent, "YOU are proof that evolution is NOT fact".
You have an excellent work ethic and are a quick learner. I don't know what the job market is like in your area but I too, urge you to check out other possibilities. You are bound to find a more comfortable fit for your talents and personality at another place of employment. Perhaps your local publically-funded technical college offers a career counselling or job placement service; I would urge you to check into that; if such services are offered, you can be tested to see what your job strengths and predilictions are, and you may find yourself being steered in an entirely different direction career wise.