I disagree full-heartedly that spells - by their inherent nature - back-fire. I believe that money spells are usually justified, are practiced by millions of magic-users worldwide, and that they do not represent an ethical gray area. It is only Neo-Pagan magical systems that prohibit and warn of money and love spells.
That being said, thoughts tend to manifest themselves. If you're sitting around fretting about your spell having negative consequences, then - like a self-fulfilling prophecy - you might get exactly what you fear.
Most likely to occur is your conflict of will and intent probably will cause the spell's energy to fizzle out, causing no results - good or bad. I would stop feeding it mental energy immediately.
If you feel strongly that you must do more magic to "remedy" the situation, i would consider a series of cleansing and blessing spiritual baths, a spiritual house-cleaning, and cleansing and blessing work on yourself and your family.