Horse is really misbehaving (warning:long)?

I have an almost 6 year old QH/mix who is really good especially for his age. I haven't been on the trails for a while since its been winter, but luckily living in Ca we have the best weather right now and its been over 60 degrees and sunny and perfect for the trails, and most of the mud is dried up. But he's been a BRAT on the trail I went three days in a row, these past three days including today. On the first day he saw a horse coming towards us and wanted to stop and stare at it but I made him keep going, and he started at the horse with fascination. Then since he walks so slow, a horse was walking behind us and gaining which made him extremely nervous, he kept stopping and looking back and started shaking his head and I could tell he wanted to buck but he didn't. Then we walked side by side for a while and he walked extremely fast. Then they left and he walked fast for a long time but they had left. On the second day we were about to go on a hill and then he saw a horse extremely far away and he stopped and stared at it and didn't want to move. So I used my crop and he REARS! agh! three times but only like 5 inches high. I made him keep going we were halfway up the hill when the horse was closer so again he stopped and stared, i asked him with my legs and he turned around started shaking his head and gave a couple of mini bucks which unseated me and I almost fell since we were on the hill, so I hopped off and walked him for a ways got back on and he was an angel the rest of the ride. Got a little nervous when he heard another horse whinny but didn't react in a bad way. Now today he didn't want to go through a mud puddle and reared (only 5 inches again) twice and I kicked him really hard after that and made him march through the mud. Then he stopped before the hill and didn't want to go so I used my crop and he kicked out his back leg. Then he went, then before another hill he turned around and gave one rear and a couple of mini bucks, but we continued on. And on the hills he stopped a lot and he kicked out his back leg a couple more times. This is so unlike him! Normally when he acts up on the trail its going downhill and he'll try to trot or do mini bucks or shake his head but then he stops easily. When we went downhill all three times he was on a complete loose rein and was very good, better than usual. And going home he only walked slightly faster and was on a loose rein too. I'll ask my trainer what she thinks but I won't see her until she comes on Thursday and wanted your opinions before then. I'm wondering if this might be pain related since it mostly happens going uphill or right before we go on it. He had his teeth floated in September, he got a new saddle in August which was checked last month and still fits great. I rode with a new pelham these last few days but its the exact same pelham I've been using just a new one. Thanks for the input, and sorry for the length of this.