Faint line. When will it darken.

Hi everyone just wondering can you help me. So on Monday I had a faint line on a pregnancy test. Barely there. Then tested again on Tuesday and the line was still faint but clearly there. So this morning Wednesday tested again and line is the same as Tuesday faint but there. Just wondering when would I expect it to darken. Digital says not pregnant. I'm 3 days late for period but only ovulated 13 days ago. I usually get my period latest day 30 and this is day 33. Thanks in advance.