Can I be pregnant again?!

I am a mother of 3, a 9 and 5 year old and an 11 month old. You would think I'd be certain by now if I thought I was pregnant BUT I'm not. About 3 weeks ago I my abdomin very low on the right was extremely painful to the touch and felt sore, as if I had pulled a muscle or been punched. Fast forward 3 weeks to now and I swear yesterday and this morning I am feeling kicks when I sit down, only very low on the right side, I mean very low. I just got off my period less than a week ago. I don't have any other symptoms either. I usually have sore breasts but I am still nursing so I wondered if that could mask it. I am headed to the store shortly for a pregnancy test! But was just wondering if anyone had experienced this.