Mental health issues affecting my relationship

[CarolAird]

Hi
I have been with my DP for nearly a year and we've had some tough times but we're generally okay.
Both of us suffer from depression (and are both on ADs and have a past (current in my case) issue with self harming) so this can make things hard for us sometimes.
However for a while I've been wondering if this is actually what I want - sometimes I get in such a state and think that breaking up with DP would be the best option and would solve all my issues and other times I'm totally, utterly infatuated. These phases can literally be minutes apart. I buy DP gifts I can't necessarily afford just because I want them to be happy with me.
I'm not really sure what I'm asking but I've read that these extremes of wanting to break up and be alone (along with other self destructive thoughts) and then feelings off euphoria and love minutes later are symptoms of borderline personality disorder. I've had these feelings in my other romantic relationship too but this is my first 'proper' relationship and I really want to make it work because DP is lovely.

I feel so guilty because when I'm having these feelings of breaking up and being alone, I discuss them with DP who then obviously thinks I am unhappy with the relationship but I'm not.

This is just a very confusing situation for both me and DP