Clomid Question!

laura
So I am in my TWW from my second round of clomid. my first round was in March and I suffered with every symptom going! on day 31 of my cycle I started bleeding, which lasted for 2-3 days, which I believe was my period. I then started my second cycle and my next period is due May 10th. 
my question is, ever since that period, my tummy has been really hard. I'm not bloated because I don't feel it, but it's hard all the time, especially when I stand up. 
Has anyone else had this? has anyone later found out they're pregnant from a similar situation? 
I thought I was pregnant but took a test about a week ago & was negative.