Severe Constipation, Need Help!

I started having constipation about 4 weeks ago. When I say constipation, I mean less frequent stools and the quantity of stool is very poor.

In addition, I've been belching a lot. This is likely due to the fact I'm constipated and the gas is going up rather than down from what my doctor told me.

My constipation is pretty bad in terms of going to the bathroom and being backed up. But, not bad enough where I am in pain down there or anywhere else.

My worry is the duration of these symptoms. I am also worried that when I do go to the bathroom, it's either watery loose or flat stools that are very light brown in color.

That said, I've been on Miralax daily, stopped drinking mountain dew and started drinking lots and lots of water. I am also taking stool softener such as Colace 100mg 3 times a day for the past couple of days.

The other day, I took a full bottle of Magnesium Citrix, which only produced lots of liquid and didn't free me up.

So, i'm worried I have a tumor. Should I now start considering X-Rays, CT Scans and possible colonoscopies?