Lighter line?? Opinions please!

I am 16 dpo and I just took a test this morning (bottom test with pink letters) and it looks slightly lighter than yesterday's test. It's the same brand (first response) but it looks like a different test. I've had somewhat painful cramping for the past few days and last night I had a lot of cramping. I haven't had any bleeding. Please let me know if I should be concerned? I'd also like to hear from people who had pretty painful cramping but no bleeding.

Thanks!!!!