Positive Hpt With Bleeding

Hi all,
I had my period on 30-dec-2017 and on 05-feb-2018, I tested with hpt and got bfp. I was vey much happy, I was like crying for the bfp I got after 2 years of ttc journey for the first time. But in the evening of 05-feb-2018, I started bleeding in small amounts which increased on 6-feb-2018 but not like a normal period. For the past 2 months, I was having 28 days cycle. Today i.e. on 6-feb-2018, I again took a hpt in afternoon inspite of bleeding and it came positive and the second line was clearly visible and it showed up in a moment. I went to my OB and told about the same. He did a TVS and told me that no sac is visible and endometrium is irregular in shape but was confused. I am currently taking Letroze 2.5 and now I am confused. If its a chemical pregnancy then why I am testing positive with hpt and that too with the afternoon urine on the second day of bleeding. I am confused as I have to take letroze from second day of my periods for the next month.
My question are:
1) Should I take letroze.
2) How long HCG remain in system after chemical pregnancy.
3) Is there still a chance of me being pregnant after all these.
The bleeding I experienced was less than normal period.
Please ladies help me with your valuable suggestions. Sorry for the long post and too many questions.
It gives me so much sorrow that I cant save my first baby and lost it. Why it happened. Why God gave me false hopes with the positive hpt and then snatched those happy moments from me in a while. Why Why Why. Still I am having tears I my eyes when I am writing this.
I am posting a picture of the hpt I did on 06-feb-2018 afternoon.