I just need advice please ! anything will help

Sarah
Hi so I've been ttc for 3 months 
Every month I get a positive pregnancy test then my period comes I don't test during my period because I feel it's just a chemical 
So this month my period was due Friday the 20 
The 18th I tested very faint line positive then Thursday had some spotting then stopped I thought my period was started 
Then nothing till Friday night 
Friday night a lot of brown period like then stopped completely by Sunday morning
I usually last 5-7 days of regular flow... so I tested Sunday (yesterday and still a vvvfl positive with frer and again today same thing...
Any thoughts?? 
I'm extreamly tired and weak breast are still hurting 
Do you think it's once again another chemical?