Please believe me; I really love you.
或
Please believe me, I really do love you.
这里 do 是助动词,有给句子强调性语气的作用。
please believe in me that I really love you
please believe in me that I really /do love you so much !!非常爱!!
还有就是please trust me that I really /do love you !这些都是标准的翻译!请相信都是我真的爱你!