so confused

So usually I get my period every 19 days, starting from the end of my period to the beginning of the next, it's like clock work, never late and never early, and it's now day 23 and I'm 3 days late and no sign of period, other then some really watery discharge 
And about 2 weeks ago I had super sore nipples and boobs to the point if I touched them I'd cry, I've eaten everything in the house and I drink more water then normal 
I'm like 80% sure I'm pregnant but not sure when to test cause I don't want it to be negative,
Help??