Afraid im losing my baby...

I need some advice. My period as of today is 4 days late so i wohld be 4 weeks and 5 days today. I have taken 4 tests in the past few days that were very faint plus a digital one that said yes so i thought everything was ok. So this morning i was going to get up and make my first doc appt and toom anothee test to make sure it the line was very faint that I could barley see it. My first pregnancy ended around this time 6 years ago bur I since have 3 healthy babies all a little over 2 years apart. We decided to just have one more. So I have had some moderate cramping today as well as some brown spotting. Along with the very faint line im worried now. Any Advice?