It isn't unusual for semen to be thick and lumpy. It depends a lot on how frequently one ejaculates. If this a drastic change from what your semen looked like before and the frequency of ejaculation hasn't changed then you may want to consult a physician. Also, if you ejaculate into a container and allow the ejaculate to sit for about 30 minutes semen should liquify and the lumpiness and thickness go away...that is normal.