weight help

I am trying to lose about 10-15lbs. Not having luck. I do stationary biking 3-4 times/week for 45min. with different speeds and levels, yoga, weights on alternating days, and walk dog. My tummy doesn't want to firm up or nor can rest of body lose weight. I am more of a snacker - and having trouble accommodating a gluten-sensitivity. Thought about protein shakes but not sure which one to look for (meat gets expensive). Finances are tight so we do our best eating healthy wise (limit boxed foods). Any suggestions would be helpful. I would like to really rev up my work out but work around back/neck injury.

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