Of course, you can't. In the sentence, “我正在+verb”, the structure is "sb + 正在 + verb". “正在” is a auxiliary verb and often used at a particular time. You use the forms '正在' and '在'(short for 正在) with a veb to form the present/past continuous tense of verbs. “正在” is a little formal, so we often "我在+verb" in spoking. 1). present continous tense 我正在吃饭。/我在吃饭。I am eating. 我正在看书。/我在看书。I am reading books. 我正在写信。/我在写信。I am wring a letter. 2). past continuous tense 昨天两点我(正)在睡觉。I was sleeping at 2 p.m. yesterday. 前天早上9点我(正)在吃饭。I was eating breakfast 9 a.m. the day before yesterday. 3). future continuous tense(seldom use this like this) 明天下午两点可能正在给孩子们讲课。I will be giving lessons to childern 2 a.m. tomorrow. "现在" means now;at the present. It is an adverb here and it is mainly used in present continuous tense. 你现在住在哪里？Where are you living now? 我现在正在吃饭。I am eating now.

You can understand 现在 as a tense and 正在 a state. 我 现在 正在 看电视。 OR 我 正在 看电视。 I am watching TV. If you want to say "I am doing something", you are more emphasizing the state hence "正在". This explanation is not very detail. But I think that is one big difference between the two.

we can use 现在 like this: 现在就 + verb 这就 + verb 现在就 + verb = 这就 + verb = "will doing in a very short time". “就” means "trend". so 现在就 means "now trend", so it means something will happen in a very short time. 我现在就/这就去学校。 ---- I will go to school in a very short time.

A supplement. 1. 【noun】 "现在" can also be used as a noun. And it means "the present; the period of time that we are in now and the things that are happening now". For example: 一直持续到现在 .... continuing right up to the present 忘掉过去，重视现在，展望未来 ... 2. 【adverb】 "现在" can also mean "at present; " as a adverb. 现在物价很高。The price is fairly high at present. 现在经济状况良好。The economy is of good state at present. 3.【adj】 "现在" with “的” form an adjective which means "present". And we can use "现在的" to describe things and people that exist now, rather than those that existed in the past or those that may exist in the future. 中国现在的经济 China's present economic 房子现在的主人 the present owner of the house

no, 现在 shows use the time while 正在 indicates the process