When to start ovulation test??

Rylie

So after my miscarriage in march I have not been on birth control because we are now ttc. So my periods use to be right on track but now with being off the pill they are all over the place. Today is the 4 day of my cycle and it's so light and usually my period lasts a whole week. When do I start ovulation tests? I'm only spotting now but not sure if it's early to start.