When can I test?

So who knew it was so hard to conceive?.. 
So my husband and I are ttc, but I have really really irregular periods. 
However for the last 8 or so days I've been feeling alittle off..
Lower back pain
Cramps 
Headache 
Occasional Tingling in my breasts and pain 
Tired 
Weird dreams 
And excess discharge 
So I don't know if I'm just imagining all this because I want to be pregnant, or if aby of these could be a sign that I am? 
But when can I test? 
I'm sick of getting negative tests it's very disheartening. 
Help!