Suggest An Effective Alternative Medicine For Nexium

I have been on Nexium for 3-4 years and it has worked fine until about 4 mos ago, it seemed it stopped working in the afternoon, so my Dr. prescribed 2 per day and I take one in morning and one mid afternoon. That seemed to help some and it does about half the time; however, some days in the evening, it seems the second pill is not really working again. Mostly I experience the symptoms early afternoon to night. I also have belching and burphing at times, especially when I have more liquids as the day progresses. Please advise.