For the past week or so, it just seems like my bass playing isnt what it could be. Jamming with friends I can never seem to make up a decent riff or fill. I hope I get over it soon
This can happen from time to time. A lot of it depends on how you are doing mentally and/or emotionally. Another problem I've had when writting was trying to avoid ripping some of my influences to much. Like Hooky (Peter Hook of Joy Division/ New Order fame, in case you didn't know,) or David J. I listen to a wide genre of music, which also helps.
I've found the easiest way to get out of "riff-block" is by playing with new people, listening to new music and not thinking or critizising myself when jamming... it's supposed to be fun, right?
Then steal little bits you like from lots of tunes to make into a new bassline for yourself 
