Taking happy pills inconsistently

How bad is it for someone on anti-depressants to be taking them inconsistently? By this I mean, going without for a day or two because they didn’t have them on them because they were on the go, or going up to 4 days without because they didn’t have anymore left and/or needed to get to the doctors for another script.

The guy I am seeing has been doing this and things are getting very rocky between us and sometimes I worry he is sleeping/seeing others. I don’t think so, because he is in SUCH a rough state. I mean breakdowns on bedroom floors, wanting to fight friends, asking me to stop loving him because he is “evil”, type of state. But he just stops talking for awhile while I know he is active and from previous relationships that’s where my mind goes. It’s hard to disconnect sometimes.