Changing a gym routine

I fear that if you keep pushing the limit higher , and add more weights it might lead to an injury . Our body is a well calibrated machine if you just want to stay fit don't push your personal recored all the time lower the limit a bit and keep on training.

From what I can tell I would be on the side of caution and start light and slowly.  Too heavy too soon and you can be injured and not be back to the gym for a while.  Start light till you are at a habit of workingout.  I would say try to slowly get into weight for around 30 days till you add much ore weight.  Of course you can up the weight a little if it is too easy but slow and steady.  Getting into shape should not be a race.

 http://eninjatraining.blogspot.com/

Make sure that the weight is always challenging.  Your technique should always be top notch however...

Remember that you should be trying to build strength and improve on each lift every singe workout...  Even if it's only one rep, 2 lbs etc.

Usually when I change a routine, I change the exercises and the muscle combinations I train. 

I suggest that you restart to a more comfortable weight. You need not ot carry heavy weights. Being Physically fit and far from sickness are most important than having a body like a bodybuilder. Find exercises where you feel comfortable and if you are bored on what you are doing then feel free to seek for new challenges.