Did you study up with the help of a unicorn who yearned for the sea? Well, it is time to tweak that knowledge a bit. I have had some help from native Japanese speakers on Lang-8 to make the following sentences into much more natural and correct sentences.
From the user meguさん, this first correction...
Instead of ぼくだけ海が好きなせいかそういう気がするかもしれない
a more correct way of saying this would be ぼくだけ海が好きなせいかそういう気がする
The reason being, せいか already has a connotation of かもしれない, so to use both in one sentence is redundant. It might be like saying, "The reason I feel like that might be because I'm the only one who lies the sea maybe."
From the user Aoiさん:
家族と一緒にいるのに、いつもぼくだけがちがう気がする。Adding だけ reinforces the idea that the speaker alone is different.
The sentence 神様に 同感してくれるものを、ぼくまで送ってくださるようにお願いしても...
might be better as 僕と同じように感じている だれかを僕のもとに送ってくださるように神様にお願いしても...
Because the unicorn is personified, instead of もの using 人 or だれか sounds better. Also notice the changes in wording (同じように感じている, 僕のもとに), and the change in sentence structure. You often hear that Japanese doesn't have a set sentence structure (besides the rule that the verb goes at the end), but the lack of official rules doesn't mean that there aren't natural inclinations to a certain order.
Looking at corrections like these can help you learn to discern what sounds more natural in your second language. If you want to see more of the corrections I received, and look a bit at the way that Lang-8 works, you can check out the entry where I mentioned the Unicorn Grammar Points. I highly recommend this free service to practice your writing skills and get some good help with your Japanese!