Last night I got a bfp but I am not sure if it's viable?

My lmp was right around new years, but it was light and only lasted three days. This week I have been feeling really off - almost daily headaches, and like my thyroid is running really low. Also my hydration pattern has been really really weird, like my electrolytes are totally whacked. Anyway, last night when I got out of the shower there was bright red blood on the towel, so since it's only been three weeks since my lmp I took a hpt and saw a faint line which I think would have been much darker had it been a fmu.
I'm cramping now but no further blood. Tomorrow I'm going to call the doctor to see if they can do an ultrasound - since my lmp was so strange I don't know how far along I would be and for bw would be accurate and I definitely want to call my endocrinologist.
I'm in shock, feeling nervous and a little scared. I can think of 10 reasons why we're - I'm - not ready for #2 but am praying to gracefully submit to God's will for us.