Possible EARLY miscarriage? Clear bubble.

My period was 4 days late. I had super light pink spotting for about a day then it stopped. I thought it might've been implantation bleeding. Tested this morning and it was negative. AF showed up light at first with cramps in my lower back and stomach. Has anyone ever had a clear bubble during their period? What is it? I gently touched it and it didn't pop.. it felt springy and weird. Sorry for the pictures.