What statistical test do i need to run?

Hi there folks,

I'm having a little difficulty choosing what statistical test i need to run,
I've conducted a series of behavioural experiments, that involves three different groups; yet all have the same individuals.
The trials are based around recording behaviour both before and after the introduction of a stimulus. But the three 'groups' data varies, and i need to understand how to compare them.
I've tried running a Wilcoxon test, however this test does not take into account any behaviour that is 0. (such as seconds spent in this behaviour).

Thank-you in advance :).