Affect is a verb – “to affect” – meaning to influence or have an impact on something. Effect is the noun – “an effect (a positive or a negative effect) is the result of being affected by something. There is also a verb “to effect”, which means to bring something about – “to effect a change”.

Are you affected or effected by something?

Affected can be used as a past tense verb that means influenced or changed. It can also be used as an adjective to refer to a noun that has been affected (the affected body part). Effected is a past tense verb that means brought about or achieved. It's a very subtle difference from affected.

Is something affecting me or effecting me?

Here's the short version of how to use affect vs. effect. Affect is usually a verb, and it means to impact or change. Effect is usually a noun, an effect is the result of a change.