- Bicycle fit  
Have your bike fit by a shop or a knowledgeable rider 
 - Bicycle efficiency  
Chain lubed.  Proper tire pressure.
 - Form   
I am going to assume a road. Can climb in the saddle or out.  Alternate.  A longer climb you will spend more time in the saddle. Out of the saddle hands on the drops. In the saddle hands on the top.
 - Cadence    
You will have a faster cadence in the saddle - like 60 but 40 may work for you.  Less than 40 then get to a lower gear.  For a strong rider it would be faster like 80-100.  Even out of the saddle you should be above 40.  Find what works for you but from your general description I suspect your cadence is much lower than it should be.  You may need to get lower gearing on your bike to get your cadence up.

[Video][1]


  [1]: https://www.youtube.com/watch?v=zam74qlzGtQ