Sprite Sheet animation without fancy add-ons

Hi all,

I am trying to include some sprite animations in my 2D beat-em-up/action game. I have glanced over many of the 2d sprite management add-ons in the unity store but alas I am very poor. I do not think I will use them enough to justify purchasing them. So, despite having no experience with animation, I decided to try animating sprite sheets on my own.

It has been going well so far. I have had success with basic animations upon button click and others that cycle through the sheet over time. But I've run into a problem. My artist has decided to add some frames on the basic attack animations and it no longer seems to be working the way I intended.

Here is a working version of the current animations. This is the main character's three-hit combo string:

 if  (Input.GetButtonDown("fight"))
                 {
                     atktimer = true;
                     atkreset = 0;
                     if (attackcounter <= 3)
                         attackcounter++;
                     StartCoroutine (PlayAnimation () );
                     if (attackcounter > 3)
                         attackcounter = 0;
                 }
                 
                 if (atktimer)
                 {
                     atkreset += Time.deltaTime;
                     if (atkreset - Time.deltaTime > 2f)
                     {
                         atktimer = false;
                         attackcounter = 0;
                     }
                 }
  
   IEnumerator PlayAnimation ()
     {
                 //attack1
                 if (attackcounter == 1)
                 {
                     animating = true;
                     audio.PlayOneShot(whoosh1);
                     renderer.material.mainTextureOffset = new Vector2 (0.25f, 0.5f);
                     
                     yield return new WaitForSeconds(0.5f);
 
             
                     animating = false;
                     frameanimation = 0f;
                 }
             
             
                 //attack2
                 if (attackcounter == 2)
                 {
                     animating = true;
                     audio.PlayOneShot(whoosh2);
                     renderer.material.mainTextureOffset = new Vector2 (0.75f, 0.5f);
                     
                     
             
                     yield return new WaitForSeconds(0.5f);
 
             
                     animating = false;
                 }
                 
                 //attack3
                 if (attackcounter == 3)
                 {
                     animating = true;
                     renderer.material.mainTextureOffset = new Vector2 (0.75f, 0.25f);
     
             
                     yield return new WaitForSeconds(0.5f);
             
                     animating = false;
                 }
         
     }
 

What this does is: Every time I click the attack button, the main character cycles through 3 different images on the sprite sheet, and at the end, it returns to the first one.

What I need: Since each attack now has additional frames, instead of simply changing the renderer offsets once per click, it needs to go through 2 frames before I click the button again. This is what I have attempted to solve the problem:

In update:

    if (animating)
                 {
                     frametimer += Time.deltaTime;
                 }

And in my Playanimation method:

 //attack1
                 if (attackcounter == 1)
                 {
                     animating = true;
                     audio.PlayOneShot(whoosh1);
                 if (frametimer - Time.deltaTime > 0)
                     renderer.material.mainTextureOffset = new Vector2 (0f, 0.5f);
                 if (frametimer - Time.deltaTime > 0.25f)
                     renderer.material.mainTextureOffset = new Vector2 (0.25f, 0.5f);
                     
                     yield return new WaitForSeconds(0.5f);
 
             
                     animating = false;
                     frametimer = 0f;
                 }

As you can see, I made a new timer to keep track of the smaller frames and inserted it into the larger attack command. It should switch frames as frametimer increments itself and play each frame for 0.25 seconds each. But it does not do this. Perhaps, there is some error in my structure or logic?

Thanks for reading! I would appreciate any help or general advice on sprite animation.