Worried at 8 weeks...

Melissa • Married October 2014 to most wonderful man in the world! Baby #1 born 2/8/16
I'm probably just overthinking, but I'm 8 weeks pregnant today according to LMP. EDD 10/23. I see the doctor on 3/24 because they couldn't fit me in right at 8 weeks. I have no pregnancy symptoms besides being a little tired and unmotivated at times. My boobs hurt a few weeks ago but now nothing. I feel good, no cravings or aversions, and no sickness whatsoever. Today I have some slight lower back pain. I'm worried that something might be wrong. No spotting but I'm always afraid it'll happen. Shouldn't I feel worse? This is my 1st and I want this pregnancy to stick!