Does this bottleneck? What should I do?

Your rig is very low end, particularly for gaming.
The HD6670 is marginally stronger than today's integrated skylake graphics.
Your cpu has a passmark rating of 1342 and a single thread rating of 890.

Most games depend on the performance of the single master thread; few can use more than 2-3 threads.
Updating to something like a Q6600 might be ok, But, I suspect a E8600 would be stronger

Yes, 4gb of ram is not good. Adding ram is not guaranteed to work.

What is your budget?

Here is my stock approach to resolving the cpu/gpu issue:

Some games are graphics limited like fast action shooters.
Others are cpu core speed limited like strategy, sims, and mmo.
Multiplayer with many participants tend to like many threads.

You need to find out which.
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To help clarify your CPU/GPU options, run these two tests:

a) Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.

b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
This will simulate what a lack of cpu power will do.
Conversely what a 30% improvement in core speed might do.

You should also experiment with removing one core. You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of processors to less than you have.
This will tell you how sensitive your games are to the benefits of many cores.

If your FPS drops significantly, it is an indicator that your cpu is the limiting factor, and a cpu upgrade is in order.

It is possible that both tests are positive, indicating that you have a well balanced system,
and both cpu and gpu need to be upgraded to get better gaming FPS.
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If you upgrade the graphics card, GTX750ti is not that big of a jump. You might be disappointed if you do not see big results.
Possibly, the upcoming GTX1050 would be a good card to target.
A bigger jump may require a strong psu.
What is your psu?