Possibly pregnant?Or something else?

For the past few months my period has been out of whack even though im taking birth control I missed two periods in august and September and then started getting random light periods that last 2 to 4 days.Ive gained maybe 5 pounds but was a little chubby to begin with and i feel a lump in my belly sometimes when i lay down in the right position the first two months during my missing period i felt sick to my stomach but never threw up and even now its sometimes gets irritated after eating my seemed to have enlarged slightly also I have felt weird sensations in my belly including one hard jolt.I had with a condom but i think when he pulled out and took it off it mightve leaked and then we used the same towel to clean off.Could I be almost 20 weeks and not be able to feel anything really because of my size or could it be something else?