Just need to rant. Any helpful tips for feeling happy, comment!

Just to set the scene: I had sex earlier with my SO having both taken a recreational drug and it wearing off (no judgement please, many people do it occasionally, without harming anyone), and shortly afterwards started to have a panic attack of sorts.
 I used to have these panic attacks very obviously at the beginning of my relationship with my SO but that was down to other things. 
I have been feeling pretty terrible lately, a mixture of work related incidents, relationship things (nothing serious) and generally have a less than positive outlook on my life over the last couple of weeks. Sure to everyone else I seem just like the happy go-lucky girl I always am but I don't feel quite like that on the inside. 
This is the first time in a long time I have felt even remotely suicidal and even now having calmed down and talked myself into sense I feel ridiculous for this whole over-dramatic outpouring but it's still niggling in the back of my head how unhappy I feel. 
Apologies for the length of this. I just needed to write my brains ramblings somewhere for the time being (this might not even make sense) I guarantee that in the morning I wake up and think this all ridiculous. But hey, 2:30am thoughts right?