Is it ok to periodically have yellowish chunky seamen if you've never actually had sex only masterbation?

Yes. It can be normal for semen to vary in consistency and color (clear, opaque, white, cream, yellow tinged) depending on your hydration, health, diet, etc. Blood tinged or streaked semen should be evaluated. However, stds can be transmitted through oral sex, too. So if you have had any contact with another's body fluids, you should consider testing.
Yes. Semen can have different constistencies that wil vary from time to time in the same patient. It can also change color slightly from white to off-white or yellow and is still usually of no clinical consequence in the abcense of other symptoms.