HELP!

I had protected sex with my boyfriend and he pulled out last week. I was ovulating when we did. I stopped ovualting 4 days ago and my period is supposed to come in 9 days. Yesterday I had light brown spotting and discomfort in my stomach. Today I have darker brown spotting with discomfort in my stomach. Besides that I have no sore breasts or nauseous. Can this be implantion bleeding?