really could do with some advice!!!!

Victoria
Hi everyone!
I test positive pregnancy the day before my missed period on 10th January but line was very very faint! It took a couple of weeks for the line to get dark it was really light. Adventually got really dark!
I've had 2 scans already and seen heart beat 1 week ish ago as I've suffered from misscarridges and had cramps. 
We came away to america for 8 days travelling was sick 2 times but apart from that I felt fine! I'm now 8 weeks and 4 days.
I had some pregnancy tests with me and decided to take them just to check (couldn't help myself) and although I got a line straight away it wasn't as dark as the last time I tested 3 weeks ago! I expected it to be darker then the test line like last time but was lighter! I didn't have much urine tho!
Is this a bad sign? We fly back from america tonight and my next scan is in 2 days but was wondering if I'm being silly and panicking over nothing! I'm scared to death of losing my squiggles! Any advice would be approached xxxxxx