Normally I focus on the tactile sensations on my upper lip when doing meditation. I tend to feel tactile sensations of the breath there. But when I try to stay one pointed on one specific sensation on one spot, it tends to disappear, and another sensation appears somewhere else, making it harder for me to concentrate on that spot. Or when I try to focus on that sensation, other sensations around the desired area of focus tend to pop up and distract me from focusing on my object, thus ruining my focus.

Should I just force my focus there?

This is really confusing for me. Please help.
Thanks

Kinda' depends on what you want to do. What do you want to do?

Focused attention and concentration on the breath will build concentration, aka samatha, and lead to jhanas.

Noticing that sensations arise and vanish and move around and change on their own will build insights, is vipassana, and leads to the stages of insight.

Why are you practicing? What are your goals for meditation?

Daniel

My goal is to reach the samatha jhanas, so I want to build my concentration. So I am trying to do samadha meditation by using this technique.
I'm practicing meditation because I have heard that meditation can help change your life significantly, especially once you are able to reach jhana.