You may need to rethink your priorities somewhat. We do have to meet our legitimate obligations, and sometimes a salary doesn't allow for too much charity. Still, Scripture is so clear on the necessity of almsgiving (see Tobit) and sacrifice that we have to be very rigorous in evaluating our response to God's call. Even if we have no money left after paying our bills, we can tithe time if that's all we have by volunteering for some worthy cause. We do need to tithe, though.