Serena - was it dark or brown blood; or was it fresh red blood? It's not uncommon to bleed during pregnancy; even during the later stages. Most GPs or caregivers usually encourage you to contact them if the blood is 'new' or a pink/red colour.
I know this sounds weird, but when you had those cramps last night...were you constipated? It's possible you might have been straining, hence the small amount of blood. It's certainly happened to me before and so far, everything is fine here too.
Seriously though, if you're concerned and you do know best; contact your caregiver. The worst they can say is 'there's nothing to be concerned about'.
