Pilot reported a NMAC while on final approach at F70 non towered airport during a training flight. Pilot performed a go-around and continued to landing.

Narrative

VFR flight from ZZZ to F70. Upon departure from ZZZ; headed southeast to setup for an entry to the traffic pattern for F70. Listened to F70 AWOS. Tuned to CTAF and listened to traffic to verify the active Runway 18 (left traffic). There appeared to be at least 2; maybe 3; aircraft in the pattern at the time. Approximately 4 miles southeast of F70; announced intentions on CTAF and entered the traffic pattern on the 45 for left downwind to Runway 18. Upon entering the downwind at TPA of approximately 1;500 ft.; announced position of downwind and proceeded to reduce speed and begin setup for landing. Heard an aircraft in the pattern ahead beginning to turn base to 18. Did not have the aircraft in sight. Began base turn for Runway 18; announced position and proceeded complete landing setup (full flaps; speed 90 kts; lights; etc.). Began turn base to final and announced position on CTAF. The turn was approximately 2 miles out from Runway 18. As I was coming out of the base to final turn; observed; what I think was Aircraft Y; cross the hold short line and line up for takeoff on 18. As I was on short final at the time; made the decision to abort the approach and proceeded to go missed on an initial heading of 180. After applying full power and retracting flaps; turned slightly to the right to side-step to not directly overfly the runway. Proceeded to climb and at midfield turned southwest to avoid traffic. Later I found out that when I was on final there was also another Aircraft Z also on final at a lower altitude that I was unaware of; and according to the pilot in Aircraft Z; my wheels came very close to his aircraft. As Aircraft Z was at a lower altitude; I could not see the aircraft and had not heard (or possibly missed) any position reports on its location. As I do not recall hearing any position reports from Aircraft Z; I can only assume that the plane was on an extended downwind leg before turning base and ended up at a lower altitude on final when I proceeded my base turn which was likely put me on a path too close to the other aircraft. Although I was following all standard procedures for landing at an untowered airport; I never had Aircraft Z in sight which was in the pattern prior to my entry. This lack of identification and situational awareness set up for a sobering situation that I have analyzed and will learn from. Based on the information I have; the primary cause was my failure to identify/confirm the traffic ahead in the pattern to insure safe distance. Another factor; as a single pilot; is that you can be easily distracted in the traffic pattern preparing for landing and missing an important position report.