lines getting darker!

I just couldn't be happier, praying my little love grows healthy and happy!! I believe I am 3 weeks 5 days, it is so early! I have been experiencing a good amount of dull cramps and some lower back pain, tender breast and just a tad bit of heartburn. Any advice for the first few weeks? This will be our first baby and I would love to have as much insight as possible! I'll be calling my OB tomorrow!