Can you get possessed by evil spirits if you are doing white magic or wicca?

If you are a believer in that sort of things then I'm not going to lie to you, yes, you can. I know people who have been through this sort of thing and have had to have their houses cleansed. One of my friends aunts is a ghost whisperer.

Witches who do not cast the circle properly (when it is necessary) are at a high risk of getting possessed.

Witches who work with Goetia, or those who summon spirits often, or those who communicate with spirits using Ouija-boards, mediums etc. have a risk of possession.

If you work with lesser entities, you shouldn't work alone and you could be able to banish them at the drop of a hat.

If someone does their magic without the help of lesser entities or spirits, and uses sources of energy such as Natural energies, Personal Life force, Crystals etc. have a very low possibility of getting possessed. Casting the circle properly and not lighting candles on bare floor (using small candle stands) minimize the such risks. Protective amulets, talismans and banishing rituals are added protection for an occultist.

A Pagan Perspective.I have been an ethical practitioner of magic for more than 40 years, and I can say with a fair amount of certainty, that the conscientious and ethical practice of magic and witchcraft does not put you in danger from evil spirits.

The belief that magic and its practice, is basically wrong/evil/bad is usually espoused by those with little true knowledge or understanding of the craft.

Most practitioners are good/honest/caring people who follow one of many spiritual paths that are not that much different from other spiritual paths.

Outsiders, dabblers and the uninitiated (by that I mean the uninformed) can and often do get themselves into difficulties by not following the basic rules, not being honest about their motivations and goals, or undertaking works they did not write themselves and/or research carefully enough to be certain of the outcome.