Should I start looking for another job?

I absolutely love my current job! I was hired as a full-time sales associate, however as of the past month or so, I've been getting part-time hours. At first I was told it was because corporate wanted to cut our stores hours (I think we have too many people!) and this week my assistant manager said we need to start fighting for hours 0.0 It makes me really nervous! Another co-worker has already gotten a second job. I feel like I should too, but I still want to be available to this job, but the hours are ALWAYS different! So I wouldn't know what to put as my availability, and I don't want to feel like I'm letting the store manager down. But I need $$, I have a bill in collections from being unemployed for a year. And other big bills.