Need advice about postnatal depression

So I gave birth to my 3rd child in February (other two are 4 and nearly 2) I suffered postnatal depression and anxiety with those 2 as well. I was on 120mg of sertraline after the birth of my second child hit decided to stop them after a few months. My first 2 were premature this time I had a full term baby so it was a complete different experience, I have good and bad days right now, good days aren't the best but I'm able to get up get dressed and feel a bit normal but when I have had days, I'll do anything to try and pick a fight with my partner and the slightest thing will push me over the edge. I'll say anything to hurt him and I can't control what I'm saying it's like I'm in the daze and when it stops either a day later or few house later I can barely remember saying the things. It's a frustration I feel like kicking and squealing and feel lile physically hurting someone. I've always wondered about the likes of bipolar or something else because of my moods but haven't a clue. Also haven't been to the doctors yet because in the UK our appointments take ages