Which itr?

Ideally it will be ITR4 but if it was temporary and you dont have docs you may go for ITR1, important if that you pay full taxes as applicable.

If I file ITR 1, is there any chance of rejection? I don't want to complicate things. At present, m receiving salary, although a professional by occupation. 

If tax u/s 194J is deducted for those 3 months of professional consultancy fees, then it is better to file ITR4.

No tax was deducted for those 3 months, neither i have any salary certificate. . Only bank passbook statements show credit of income.

As per provisions of law, right form is ITR4, but if you want to show such income as salary then ITR1 can be used.

But i don't have any Form 16A, where TDS has been deducted under 194J.. on what basis, i will file ITR4? Thats my confusion. 

Basis is credit of income to your account. If tax is not deducted at source, it is the problem of the payee of income. You can still declare income and pay tax accordingly even though no form 16A is issued. But it is also imperative to know how the same is treated in the hands of payer. If tax at source is not deducted, it can mean either the amount paid is withint the limit of 30k or it is accounted as something else in the books of the payer.

Ok.. thats a big problem now.. 

Payment was 30k plus every month for those 3 months...

Okay, if you have any agreement for consultancy, then you better show it as professional income. But since the payee has not deducted tax at source, you need to pay tax on the same. If no such agreement, then you can show it as salary income.

Ok thanks.. have to look into the agreement. ..

Just tell me, if there will be any problem if i use ITR 1? And if i use ITR 1, where to put the previous income? In total income from salary or income from other sources??

You can include it under income from salary.