Ok, so I've had my heart broken recently by my girlfriend cheating on me, but I wondered if people feel that if things move too quick into a relationship, could that be a reason for some cracks to appear further down the line?

My girlfriend who is no more gave me a spare house key only two months into our relationship which struck me as odd!

Yes it's nice to trust people, but you still don't really know someone after only two months of seeing each other.