Student pilot reported a NMAC with another aircraft while in the traffic pattern at a non-towered airport.

Narrative

I was on a solo cross country to ZZZ.While operating in the pattern ZZZ airport on Left crosswind; another aircraft came close to my aircraft from the right. I never saw the other conflict aircraft; until it came suddenly very close to my aircraft.The conflict aircraft was apparently in a self-modified non-standard location coming into the pattern; straight; from the right; of normal left crosswind traffic. The conflict aircraft was on an incorrect long straight pre-downwind.I was safely maneuvering my aircraft in the appropriate standard pattern operation and diligently looking out for all traffic; while communicating my intentions and position; and listening for other traffic in the pattern.Suddenly; the conflict aircraft that was in a nonstandard pattern location came very close to my aircraft. I maneuvered my aircraft to avoid.Inadvertently we came within a couple of hundred feet of each other. To further complicate the issue;the CTAF being used is on the same frequency as several other airports; and the radio congestion was heavy between the different airports and aircraft. I then continued to complete my flight safely.I believe that this situation would not have happened if: 1. The conflict aircraft; who was in the nonstandard location should have appropriately exercised the requirement to see and avoid. 2. The conflict aircraft should have entered the pattern using standard pattern entry procedures.3. If the conflict aircraft could not maintain a safe distance; then they should not have entered the pattern and repositioned themselves to standard pattern entry and comply with standard pattern procedures.4. If CTAF frequencies were specific to an individual airport and not commonly used by adjacent airports; then this could have potentially enhanced situational awareness.